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 $86.26   9.821%   $94.7316   $94.73   $94.75   $94.70  
  Purchase #2 $97.68   9.286%   $106.7506   $106.75   $106.75   $106.80  
  Purchase #3 $205.57   13.591%   $233.509   $233.51   $233.50   $233.50  
  Purchase #4 $206.39   3.162%   $212.9161   $212.92   $212.90   $212.90  
  Purchase #5 $84.93   13.820%   $96.6673   $96.67   $96.65   $96.70  
  Purchase #6 $118.31   11.730%   $132.1878   $132.19   $132.20   $132.20  
  Purchase #7 $152.32   3.732%   $158.0046   $158.00   $158.00   $158.00  
  7 purchase totals = $951.46       $1,034.7670   $1,034.77   $1,034.75   $1,034.80