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 $54.86   5.459%   $57.8548   $57.85   $57.85   $57.90  
  Purchase #2 $214.54   4.406%   $223.9926   $223.99   $224.00   $224.00  
  Purchase #3 $191.60   10.344%   $211.4191   $211.42   $211.40   $211.40  
  Purchase #4 $64.96   3.191%   $67.0329   $67.03   $67.05   $67.00  
  Purchase #5 $73.65   8.810%   $80.1386   $80.14   $80.15   $80.10  
  Purchase #6 $60.27   8.480%   $65.3809   $65.38   $65.40   $65.40  
  Purchase #7 $88.82   7.451%   $95.438   $95.44   $95.45   $95.40  
  7 purchase totals = $748.70       $801.2569   $801.25   $801.30   $801.20