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 $168.28   11.611%   $187.819   $187.82   $187.80   $187.80  
  Purchase #2 $91.97   12.361%   $103.3384   $103.34   $103.35   $103.30  
  Purchase #3 $194.87   9.613%   $213.6029   $213.60   $213.60   $213.60  
  Purchase #4 $165.66   6.454%   $176.3517   $176.35   $176.35   $176.40  
  Purchase #5 $233.56   5.536%   $246.4899   $246.49   $246.50   $246.50  
  Purchase #6 $48.46   5.828%   $51.2842   $51.28   $51.30   $51.30  
  Purchase #7 $54.34   4.629%   $56.8554   $56.86   $56.85   $56.90  
  7 purchase totals = $957.14       $1,035.7415   $1,035.74   $1,035.75   $1,035.80