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 $179.92   9.517%   $197.043   $197.04   $197.05   $197.00  
  Purchase #2 $95.51   11.323%   $106.3246   $106.32   $106.30   $106.30  
  Purchase #3 $216.79   7.151%   $232.2927   $232.29   $232.30   $232.30  
  Purchase #4 $30.94   10.576%   $34.2122   $34.21   $34.20   $34.20  
  Purchase #5 $170.43   12.506%   $191.744   $191.74   $191.75   $191.70  
  Purchase #6 $197.35   5.287%   $207.7839   $207.78   $207.80   $207.80  
  Purchase #7 $159.57   13.368%   $180.9013   $180.90   $180.90   $180.90  
  7 purchase totals = $1,050.51       $1,150.3017   $1,150.28   $1,150.30   $1,150.20