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 $169.59   13.774%   $192.9493   $192.95   $192.95   $192.90  
  Purchase #2 $177.98   9.558%   $194.9913   $194.99   $195.00   $195.00  
  Purchase #3 $87.87   7.722%   $94.6553   $94.66   $94.65   $94.70  
  Purchase #4 $246.86   7.760%   $266.0163   $266.02   $266.00   $266.00  
  Purchase #5 $75.84   3.599%   $78.5695   $78.57   $78.55   $78.60  
  Purchase #6 $25.72   7.299%   $27.5973   $27.60   $27.60   $27.60  
  Purchase #7 $161.66   10.338%   $178.3724   $178.37   $178.35   $178.40  
  7 purchase totals = $945.52       $1,033.1514   $1,033.16   $1,033.10   $1,033.20