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 $53.30   7.405%   $57.2469   $57.25   $57.25   $57.20  
  Purchase #2 $219.72   10.837%   $243.5311   $243.53   $243.55   $243.50  
  Purchase #3 $233.42   10.273%   $257.3992   $257.40   $257.40   $257.40  
  Purchase #4 $14.53   10.757%   $16.093   $16.09   $16.10   $16.10  
  Purchase #5 $138.81   6.362%   $147.6411   $147.64   $147.65   $147.60  
  Purchase #6 $154.66   3.249%   $159.6849   $159.68   $159.70   $159.70  
  Purchase #7 $62.38   10.351%   $68.837   $68.84   $68.85   $68.80  
  7 purchase totals = $876.82       $950.4332   $950.43   $950.50   $950.30