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 $120.87   3.475%   $125.0702   $125.07   $125.05   $125.10  
  Purchase #2 $234.82   4.208%   $244.7012   $244.70   $244.70   $244.70  
  Purchase #3 $218.71   11.125%   $243.0415   $243.04   $243.05   $243.00  
  Purchase #4 $62.96   4.194%   $65.6005   $65.60   $65.60   $65.60  
  Purchase #5 $70.96   8.516%   $77.003   $77.00   $77.00   $77.00  
  Purchase #6 $148.84   5.281%   $156.7002   $156.70   $156.70   $156.70  
  Purchase #7 $67.94   11.270%   $75.5968   $75.60   $75.60   $75.60  
  7 purchase totals = $925.10       $987.7134   $987.71   $987.70   $987.70