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 $119.39   4.823%   $125.1482   $125.15   $125.15   $125.10  
  Purchase #2 $147.88   9.537%   $161.9833   $161.98   $162.00   $162.00  
  Purchase #3 $238.88   3.298%   $246.7583   $246.76   $246.75   $246.80  
  Purchase #4 $56.81   3.158%   $58.6041   $58.60   $58.60   $58.60  
  Purchase #5 $209.61   5.401%   $220.931   $220.93   $220.95   $220.90  
  Purchase #6 $19.27   5.341%   $20.2992   $20.30   $20.30   $20.30  
  Purchase #7 $32.74   10.314%   $36.1168   $36.12   $36.10   $36.10  
  7 purchase totals = $824.58       $869.8409   $869.84   $869.85   $869.80