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 $227.61   8.103%   $246.0532   $246.05   $246.05   $246.10  
  Purchase #2 $99.29   5.546%   $104.7966   $104.80   $104.80   $104.80  
  Purchase #3 $74.76   7.171%   $80.121   $80.12   $80.10   $80.10  
  Purchase #4 $187.79   7.863%   $202.5559   $202.56   $202.55   $202.60  
  Purchase #5 $244.69   11.215%   $272.132   $272.13   $272.15   $272.10  
  Purchase #6 $99.92   4.294%   $104.2106   $104.21   $104.20   $104.20  
  Purchase #7 $39.44   11.412%   $43.9409   $43.94   $43.95   $43.90  
  7 purchase totals = $973.50       $1,053.8102   $1,053.81   $1,053.80   $1,053.80