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 $86.33   9.631%   $94.6444   $94.64   $94.65   $94.60  
  Purchase #2 $68.43   10.543%   $75.6446   $75.64   $75.65   $75.60  
  Purchase #3 $156.35   10.429%   $172.6557   $172.66   $172.65   $172.70  
  Purchase #4 $93.61   3.764%   $97.1335   $97.13   $97.15   $97.10  
  Purchase #5 $200.42   3.625%   $207.6852   $207.69   $207.70   $207.70  
  Purchase #6 $237.95   3.429%   $246.1093   $246.11   $246.10   $246.10  
  Purchase #7 $206.55   12.699%   $232.7798   $232.78   $232.80   $232.80  
  7 purchase totals = $1,049.64       $1,126.6525   $1,126.65   $1,126.70   $1,126.60