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 $241.47   8.693%   $262.461   $262.46   $262.45   $262.50  
  Purchase #2 $230.73   3.478%   $238.7548   $238.75   $238.75   $238.80  
  Purchase #3 $11.45   12.322%   $12.8609   $12.86   $12.85   $12.90  
  Purchase #4 $50.75   7.437%   $54.5243   $54.52   $54.50   $54.50  
  Purchase #5 $68.89   5.681%   $72.8036   $72.80   $72.80   $72.80  
  Purchase #6 $21.33   6.198%   $22.652   $22.65   $22.65   $22.70  
  Purchase #7 $229.77   6.188%   $243.9882   $243.99   $244.00   $244.00  
  7 purchase totals = $854.39       $908.0448   $908.03   $908.00   $908.20