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 $93.46   11.284%   $104.006   $104.01   $104.00   $104.00  
  Purchase #2 $213.31   10.629%   $235.9827   $235.98   $236.00   $236.00  
  Purchase #3 $205.25   11.389%   $228.6259   $228.63   $228.65   $228.60  
  Purchase #4 $152.44   10.755%   $168.8349   $168.83   $168.85   $168.80  
  Purchase #5 $144.42   10.532%   $159.6303   $159.63   $159.65   $159.60  
  Purchase #6 $204.37   13.516%   $231.9926   $231.99   $232.00   $232.00  
  Purchase #7 $16.78   6.261%   $17.8306   $17.83   $17.85   $17.80  
  7 purchase totals = $1,030.03       $1,146.9030   $1,146.90   $1,147.00   $1,146.80