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 $148.94   5.587%   $157.2613   $157.26   $157.25   $157.30  
  Purchase #2 $83.52   5.347%   $87.9858   $87.99   $88.00   $88.00  
  Purchase #3 $80.85   5.744%   $85.494   $85.49   $85.50   $85.50  
  Purchase #4 $18.96   6.450%   $20.1829   $20.18   $20.20   $20.20  
  Purchase #5 $205.51   8.869%   $223.7367   $223.74   $223.75   $223.70  
  Purchase #6 $123.62   8.809%   $134.5097   $134.51   $134.50   $134.50  
  Purchase #7 $233.69   4.295%   $243.727   $243.73   $243.75   $243.70  
  7 purchase totals = $895.09       $952.8974   $952.90   $952.95   $952.90