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 $89.75   8.368%   $97.2603   $97.26   $97.25   $97.30  
  Purchase #2 $195.86   5.367%   $206.3718   $206.37   $206.35   $206.40  
  Purchase #3 $145.28   12.186%   $162.9838   $162.98   $163.00   $163.00  
  Purchase #4 $183.66   7.243%   $196.9625   $196.96   $196.95   $197.00  
  Purchase #5 $159.31   5.785%   $168.5261   $168.53   $168.55   $168.50  
  Purchase #6 $150.91   6.340%   $160.4777   $160.48   $160.50   $160.50  
  Purchase #7 $120.83   4.650%   $126.4486   $126.45   $126.45   $126.40  
  7 purchase totals = $1,045.60       $1,119.0308   $1,119.03   $1,119.05   $1,119.10