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 $62.47   8.191%   $67.5869   $67.59   $67.60   $67.60  
  Purchase #2 $108.31   5.113%   $113.8479   $113.85   $113.85   $113.80  
  Purchase #3 $56.51   11.768%   $63.1601   $63.16   $63.15   $63.20  
  Purchase #4 $23.32   7.825%   $25.1448   $25.14   $25.15   $25.10  
  Purchase #5 $193.98   5.340%   $204.3385   $204.34   $204.35   $204.30  
  Purchase #6 $13.30   6.226%   $14.1281   $14.13   $14.15   $14.10  
  Purchase #7 $197.30   3.273%   $203.7576   $203.76   $203.75   $203.80  
  7 purchase totals = $655.19       $691.9639   $691.97   $692.00   $691.90