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 $148.82   8.392%   $161.309   $161.31   $161.30   $161.30  
  Purchase #2 $87.95   5.560%   $92.84   $92.84   $92.85   $92.80  
  Purchase #3 $199.46   12.806%   $225.0028   $225.00   $225.00   $225.00  
  Purchase #4 $79.79   11.248%   $88.7648   $88.76   $88.75   $88.80  
  Purchase #5 $87.97   13.184%   $99.568   $99.57   $99.55   $99.60  
  Purchase #6 $118.34   4.163%   $123.2665   $123.27   $123.25   $123.30  
  Purchase #7 $239.86   9.628%   $262.9537   $262.95   $262.95   $263.00  
  7 purchase totals = $962.19       $1,053.7048   $1,053.70   $1,053.65   $1,053.80