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 $65.27   13.329%   $73.9698   $73.97   $73.95   $74.00  
  Purchase #2 $203.25   7.431%   $218.3535   $218.35   $218.35   $218.40  
  Purchase #3 $197.62   4.709%   $206.9259   $206.93   $206.95   $206.90  
  Purchase #4 $107.49   5.199%   $113.0784   $113.08   $113.10   $113.10  
  Purchase #5 $223.86   4.551%   $234.0479   $234.05   $234.05   $234.00  
  Purchase #6 $160.30   3.497%   $165.9057   $165.91   $165.90   $165.90  
  Purchase #7 $159.94   13.156%   $180.9817   $180.98   $181.00   $181.00  
  7 purchase totals = $1,117.73       $1,193.2629   $1,193.27   $1,193.30   $1,193.30