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 $70.95   4.687%   $74.2754   $74.28   $74.30   $74.30  
  Purchase #2 $169.87   10.258%   $187.2953   $187.30   $187.30   $187.30  
  Purchase #3 $189.68   10.672%   $209.9226   $209.92   $209.90   $209.90  
  Purchase #4 $156.99   7.776%   $169.1975   $169.20   $169.20   $169.20  
  Purchase #5 $167.85   8.428%   $181.9964   $182.00   $182.00   $182.00  
  Purchase #6 $65.96   10.446%   $72.8502   $72.85   $72.85   $72.90  
  Purchase #7 $169.88   6.699%   $181.2603   $181.26   $181.25   $181.30  
  7 purchase totals = $991.18       $1,076.7977   $1,076.81   $1,076.80   $1,076.90