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 $196.48   11.767%   $219.5998   $219.60   $219.60   $219.60  
  Purchase #2 $17.96   7.413%   $19.2914   $19.29   $19.30   $19.30  
  Purchase #3 $60.47   7.435%   $64.9659   $64.97   $64.95   $65.00  
  Purchase #4 $177.86   12.245%   $199.639   $199.64   $199.65   $199.60  
  Purchase #5 $102.88   4.733%   $107.7493   $107.75   $107.75   $107.70  
  Purchase #6 $81.62   7.353%   $87.6215   $87.62   $87.60   $87.60  
  Purchase #7 $123.99   8.151%   $134.0964   $134.10   $134.10   $134.10  
  7 purchase totals = $761.26       $832.9633   $832.97   $832.95   $832.90