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 $87.51   7.874%   $94.4005   $94.40   $94.40   $94.40  
  Purchase #2 $101.53   13.751%   $115.4914   $115.49   $115.50   $115.50  
  Purchase #3 $138.46   6.717%   $147.7604   $147.76   $147.75   $147.80  
  Purchase #4 $140.63   7.809%   $151.6118   $151.61   $151.60   $151.60  
  Purchase #5 $209.89   5.728%   $221.9125   $221.91   $221.90   $221.90  
  Purchase #6 $162.28   10.151%   $178.753   $178.75   $178.75   $178.80  
  Purchase #7 $219.46   12.333%   $246.526   $246.53   $246.55   $246.50  
  7 purchase totals = $1,059.76       $1,156.4556   $1,156.45   $1,156.45   $1,156.50