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 $57.67   7.434%   $61.9572   $61.96   $61.95   $62.00  
  Purchase #2 $170.75   8.227%   $184.7976   $184.80   $184.80   $184.80  
  Purchase #3 $114.27   9.585%   $125.2228   $125.22   $125.20   $125.20  
  Purchase #4 $95.99   10.536%   $106.1035   $106.10   $106.10   $106.10  
  Purchase #5 $211.87   3.702%   $219.7134   $219.71   $219.70   $219.70  
  Purchase #6 $18.46   12.284%   $20.7276   $20.73   $20.75   $20.70  
  Purchase #7 $20.68   10.178%   $22.7848   $22.78   $22.80   $22.80  
  7 purchase totals = $689.69       $741.3069   $741.30   $741.30   $741.30