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 $57.84   7.537%   $62.1994   $62.20   $62.20   $62.20  
  Purchase #2 $250.46   12.388%   $281.487   $281.49   $281.50   $281.50  
  Purchase #3 $17.86   10.453%   $19.7269   $19.73   $19.75   $19.70  
  Purchase #4 $235.34   13.700%   $267.5816   $267.58   $267.60   $267.60  
  Purchase #5 $82.94   12.244%   $93.0952   $93.10   $93.10   $93.10  
  Purchase #6 $190.84   7.784%   $205.695   $205.70   $205.70   $205.70  
  Purchase #7 $196.49   10.190%   $216.5123   $216.51   $216.50   $216.50  
  7 purchase totals = $1,031.77       $1,146.2974   $1,146.31   $1,146.35   $1,146.30