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 $83.82   12.713%   $94.476   $94.48   $94.50   $94.50  
  Purchase #2 $153.98   7.656%   $165.7687   $165.77   $165.75   $165.80  
  Purchase #3 $147.72   13.809%   $168.1187   $168.12   $168.10   $168.10  
  Purchase #4 $246.61   3.699%   $255.7321   $255.73   $255.75   $255.70  
  Purchase #5 $87.55   5.823%   $92.648   $92.65   $92.65   $92.60  
  Purchase #6 $129.63   12.435%   $145.7495   $145.75   $145.75   $145.70  
  Purchase #7 $190.69   6.512%   $203.1077   $203.11   $203.10   $203.10  
  7 purchase totals = $1,040.00       $1,125.6007   $1,125.61   $1,125.60   $1,125.50