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 $33.82   9.621%   $37.0738   $37.07   $37.05   $37.10  
  Purchase #2 $191.69   13.313%   $217.2097   $217.21   $217.20   $217.20  
  Purchase #3 $56.51   9.636%   $61.9553   $61.96   $61.95   $62.00  
  Purchase #4 $133.33   12.402%   $149.8656   $149.87   $149.85   $149.90  
  Purchase #5 $204.43   11.658%   $228.2624   $228.26   $228.25   $228.30  
  Purchase #6 $55.29   12.141%   $62.0028   $62.00   $62.00   $62.00  
  Purchase #7 $123.45   6.712%   $131.736   $131.74   $131.75   $131.70  
  7 purchase totals = $798.52       $888.1056   $888.11   $888.05   $888.20