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 $59.50   5.394%   $62.7094   $62.71   $62.70   $62.70  
  Purchase #2 $41.77   5.146%   $43.9195   $43.92   $43.90   $43.90  
  Purchase #3 $204.72   11.507%   $228.2771   $228.28   $228.30   $228.30  
  Purchase #4 $60.91   3.728%   $63.1807   $63.18   $63.20   $63.20  
  Purchase #5 $233.31   12.827%   $263.2367   $263.24   $263.25   $263.20  
  Purchase #6 $50.90   7.263%   $54.5969   $54.60   $54.60   $54.60  
  Purchase #7 $203.35   5.216%   $213.9567   $213.96   $213.95   $214.00  
  7 purchase totals = $854.46       $929.8770   $929.89   $929.90   $929.90