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 $87.71   8.462%   $95.132   $95.13   $95.15   $95.10  
  Purchase #2 $132.99   8.336%   $144.076   $144.08   $144.10   $144.10  
  Purchase #3 $75.86   4.371%   $79.1758   $79.18   $79.20   $79.20  
  Purchase #4 $175.64   5.542%   $185.374   $185.37   $185.35   $185.40  
  Purchase #5 $195.83   7.241%   $210.0101   $210.01   $210.00   $210.00  
  Purchase #6 $92.29   5.382%   $97.257   $97.26   $97.25   $97.30  
  Purchase #7 $228.96   9.107%   $249.8114   $249.81   $249.80   $249.80  
  7 purchase totals = $989.28       $1,060.8363   $1,060.84   $1,060.85   $1,060.90