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 $223.74   9.392%   $244.7537   $244.75   $244.75   $244.80  
  Purchase #2 $226.84   10.829%   $251.4045   $251.40   $251.40   $251.40  
  Purchase #3 $87.80   7.199%   $94.1207   $94.12   $94.10   $94.10  
  Purchase #4 $82.72   3.189%   $85.3579   $85.36   $85.35   $85.40  
  Purchase #5 $103.97   4.211%   $108.3482   $108.35   $108.35   $108.30  
  Purchase #6 $226.88   3.234%   $234.2173   $234.22   $234.20   $234.20  
  Purchase #7 $59.89   7.542%   $64.4069   $64.41   $64.40   $64.40  
  7 purchase totals = $1,011.84       $1,082.6092   $1,082.61   $1,082.55   $1,082.60