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 $203.88   3.557%   $211.132   $211.13   $211.15   $211.10  
  Purchase #2 $218.30   13.311%   $247.3579   $247.36   $247.35   $247.40  
  Purchase #3 $45.75   4.783%   $47.9382   $47.94   $47.95   $47.90  
  Purchase #4 $182.88   12.584%   $205.8936   $205.89   $205.90   $205.90  
  Purchase #5 $152.75   6.394%   $162.5168   $162.52   $162.50   $162.50  
  Purchase #6 $70.53   6.522%   $75.13   $75.13   $75.15   $75.10  
  Purchase #7 $188.30   6.366%   $200.2872   $200.29   $200.30   $200.30  
  7 purchase totals = $1,062.39       $1,150.2557   $1,150.26   $1,150.30   $1,150.20