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 $212.86   10.539%   $235.2933   $235.29   $235.30   $235.30  
  Purchase #2 $203.37   8.408%   $220.4693   $220.47   $220.45   $220.50  
  Purchase #3 $36.77   7.114%   $39.3858   $39.39   $39.40   $39.40  
  Purchase #4 $250.68   10.458%   $276.8961   $276.90   $276.90   $276.90  
  Purchase #5 $194.56   10.751%   $215.4771   $215.48   $215.50   $215.50  
  Purchase #6 $204.85   10.425%   $226.2056   $226.21   $226.20   $226.20  
  Purchase #7 $181.83   8.797%   $197.8256   $197.83   $197.85   $197.80  
  7 purchase totals = $1,284.92       $1,411.5528   $1,411.57   $1,411.60   $1,411.60