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 $211.82   5.303%   $223.0528   $223.05   $223.05   $223.10  
  Purchase #2 $230.86   6.150%   $245.0579   $245.06   $245.05   $245.10  
  Purchase #3 $92.39   5.743%   $97.696   $97.70   $97.70   $97.70  
  Purchase #4 $112.71   3.170%   $116.2829   $116.28   $116.30   $116.30  
  Purchase #5 $90.60   5.152%   $95.2677   $95.27   $95.25   $95.30  
  Purchase #6 $191.87   10.484%   $211.9857   $211.99   $212.00   $212.00  
  Purchase #7 $67.95   9.177%   $74.1858   $74.19   $74.20   $74.20  
  7 purchase totals = $998.20       $1,063.5288   $1,063.54   $1,063.55   $1,063.70