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 $68.27   11.144%   $75.878   $75.88   $75.90   $75.90  
  Purchase #2 $148.34   9.743%   $162.7928   $162.79   $162.80   $162.80  
  Purchase #3 $232.68   8.144%   $251.6295   $251.63   $251.65   $251.60  
  Purchase #4 $87.55   11.737%   $97.8257   $97.83   $97.85   $97.80  
  Purchase #5 $99.57   9.487%   $109.0162   $109.02   $109.00   $109.00  
  Purchase #6 $160.46   6.661%   $171.1482   $171.15   $171.15   $171.10  
  Purchase #7 $69.33   9.607%   $75.9905   $75.99   $76.00   $76.00  
  7 purchase totals = $866.20       $944.2809   $944.29   $944.35   $944.20