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 $59.29   10.507%   $65.5196   $65.52   $65.50   $65.50  
  Purchase #2 $166.41   4.149%   $173.3144   $173.31   $173.30   $173.30  
  Purchase #3 $222.42   6.557%   $237.0041   $237.00   $237.00   $237.00  
  Purchase #4 $99.36   5.157%   $104.484   $104.48   $104.50   $104.50  
  Purchase #5 $56.86   6.496%   $60.5536   $60.55   $60.55   $60.60  
  Purchase #6 $202.57   13.156%   $229.2201   $229.22   $229.20   $229.20  
  Purchase #7 $222.80   9.777%   $244.5832   $244.58   $244.60   $244.60  
  7 purchase totals = $1,029.71       $1,114.6790   $1,114.66   $1,114.65   $1,114.70