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 $92.60   4.449%   $96.7198   $96.72   $96.70   $96.70  
  Purchase #2 $66.70   8.618%   $72.4482   $72.45   $72.45   $72.40  
  Purchase #3 $88.91   9.829%   $97.649   $97.65   $97.65   $97.60  
  Purchase #4 $51.28   11.598%   $57.2275   $57.23   $57.25   $57.20  
  Purchase #5 $165.77   8.656%   $180.1191   $180.12   $180.10   $180.10  
  Purchase #6 $143.78   9.567%   $157.5354   $157.54   $157.55   $157.50  
  Purchase #7 $43.30   4.686%   $45.329   $45.33   $45.35   $45.30  
  7 purchase totals = $652.34       $707.0280   $707.04   $707.05   $706.80