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 $175.48   10.520%   $193.9405   $193.94   $193.95   $193.90  
  Purchase #2 $16.95   13.341%   $19.2113   $19.21   $19.20   $19.20  
  Purchase #3 $167.32   6.132%   $177.5801   $177.58   $177.60   $177.60  
  Purchase #4 $116.57   5.301%   $122.7494   $122.75   $122.75   $122.70  
  Purchase #5 $118.43   9.270%   $129.4085   $129.41   $129.40   $129.40  
  Purchase #6 $139.95   7.597%   $150.582   $150.58   $150.60   $150.60  
  Purchase #7 $135.94   9.703%   $149.1303   $149.13   $149.15   $149.10  
  7 purchase totals = $870.64       $942.6021   $942.60   $942.65   $942.50