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 $198.54   7.812%   $214.0499   $214.05   $214.05   $214.00  
  Purchase #2 $187.67   11.650%   $209.5336   $209.53   $209.55   $209.50  
  Purchase #3 $40.53   12.326%   $45.5257   $45.53   $45.55   $45.50  
  Purchase #4 $63.84   6.424%   $67.9411   $67.94   $67.95   $67.90  
  Purchase #5 $207.42   8.575%   $225.2063   $225.21   $225.20   $225.20  
  Purchase #6 $50.33   13.519%   $57.1341   $57.13   $57.15   $57.10  
  Purchase #7 $240.94   7.726%   $259.555   $259.56   $259.55   $259.60  
  7 purchase totals = $989.27       $1,078.9457   $1,078.95   $1,079.00   $1,078.80