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 $72.55   4.481%   $75.801   $75.80   $75.80   $75.80  
  Purchase #2 $96.80   6.584%   $103.1733   $103.17   $103.15   $103.20  
  Purchase #3 $129.97   3.716%   $134.7997   $134.80   $134.80   $134.80  
  Purchase #4 $141.68   6.527%   $150.9275   $150.93   $150.95   $150.90  
  Purchase #5 $201.97   11.108%   $224.4048   $224.40   $224.40   $224.40  
  Purchase #6 $62.36   4.852%   $65.3857   $65.39   $65.40   $65.40  
  Purchase #7 $6.35   10.765%   $7.0336   $7.03   $7.05   $7.00  
  7 purchase totals = $711.68       $761.5256   $761.52   $761.55   $761.50