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 $70.92   7.107%   $75.9603   $75.96   $75.95   $76.00  
  Purchase #2 $248.89   9.334%   $272.1214   $272.12   $272.10   $272.10  
  Purchase #3 $186.53   10.397%   $205.9235   $205.92   $205.90   $205.90  
  Purchase #4 $107.44   12.117%   $120.4585   $120.46   $120.45   $120.50  
  Purchase #5 $61.76   11.717%   $68.9964   $69.00   $69.00   $69.00  
  Purchase #6 $221.68   12.203%   $248.7316   $248.73   $248.75   $248.70  
  Purchase #7 $57.74   5.861%   $61.1241   $61.12   $61.10   $61.10  
  7 purchase totals = $954.96       $1,053.3158   $1,053.31   $1,053.25   $1,053.30