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 $194.47   3.614%   $201.4981   $201.50   $201.50   $201.50  
  Purchase #2 $236.85   6.104%   $251.3073   $251.31   $251.30   $251.30  
  Purchase #3 $237.42   13.306%   $269.0111   $269.01   $269.00   $269.00  
  Purchase #4 $227.44   8.669%   $247.1568   $247.16   $247.15   $247.20  
  Purchase #5 $35.28   5.838%   $37.3396   $37.34   $37.35   $37.30  
  Purchase #6 $13.82   6.667%   $14.7414   $14.74   $14.75   $14.70  
  Purchase #7 $82.41   3.230%   $85.0718   $85.07   $85.05   $85.10  
  7 purchase totals = $1,027.69       $1,106.1261   $1,106.13   $1,106.10   $1,106.10