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 $53.75   13.250%   $60.8719   $60.87   $60.85   $60.90  
  Purchase #2 $137.94   3.639%   $142.9596   $142.96   $142.95   $143.00  
  Purchase #3 $106.67   8.862%   $116.1231   $116.12   $116.10   $116.10  
  Purchase #4 $193.26   4.774%   $202.4862   $202.49   $202.50   $202.50  
  Purchase #5 $60.57   10.573%   $66.9741   $66.97   $66.95   $67.00  
  Purchase #6 $40.97   10.375%   $45.2206   $45.22   $45.20   $45.20  
  Purchase #7 $63.43   4.568%   $66.3275   $66.33   $66.35   $66.30  
  7 purchase totals = $656.59       $700.9630   $700.96   $700.90   $701.00