Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $145.82   4.822%   $152.8514   $152.85   $152.85   $152.90  
  Purchase #2 $149.31   11.497%   $166.4762   $166.48   $166.50   $166.50  
  Purchase #3 $233.51   7.755%   $251.6187   $251.62   $251.60   $251.60  
  Purchase #4 $226.47   5.461%   $238.8375   $238.84   $238.85   $238.80  
  Purchase #5 $115.67   4.777%   $121.1956   $121.20   $121.20   $121.20  
  Purchase #6 $207.36   4.504%   $216.6995   $216.70   $216.70   $216.70  
  Purchase #7 $121.73   10.481%   $134.4885   $134.49   $134.50   $134.50  
  7 purchase totals = $1,199.87       $1,282.1674   $1,282.18   $1,282.20   $1,282.20