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 $70.62   6.120%   $74.9419   $74.94   $74.95   $74.90  
  Purchase #2 $214.99   12.562%   $241.997   $242.00   $242.00   $242.00  
  Purchase #3 $150.81   4.441%   $157.5075   $157.51   $157.50   $157.50  
  Purchase #4 $193.99   9.485%   $212.39   $212.39   $212.40   $212.40  
  Purchase #5 $200.31   3.666%   $207.6534   $207.65   $207.65   $207.70  
  Purchase #6 $223.80   8.585%   $243.0132   $243.01   $243.00   $243.00  
  Purchase #7 $26.46   9.707%   $29.0285   $29.03   $29.05   $29.00  
  7 purchase totals = $1,080.98       $1,166.5315   $1,166.53   $1,166.55   $1,166.50