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 $53.82   12.622%   $60.6132   $60.61   $60.60   $60.60  
  Purchase #2 $205.80   12.314%   $231.1422   $231.14   $231.15   $231.10  
  Purchase #3 $70.71   5.315%   $74.4682   $74.47   $74.45   $74.50  
  Purchase #4 $217.56   3.871%   $225.9817   $225.98   $226.00   $226.00  
  Purchase #5 $180.70   13.256%   $204.6536   $204.65   $204.65   $204.70  
  Purchase #6 $134.84   11.215%   $149.9623   $149.96   $149.95   $150.00  
  Purchase #7 $184.44   12.582%   $207.6462   $207.65   $207.65   $207.60  
  7 purchase totals = $1,047.87       $1,154.4674   $1,154.46   $1,154.45   $1,154.50