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 $92.69   9.145%   $101.1665   $101.17   $101.15   $101.20  
  Purchase #2 $184.52   12.293%   $207.203   $207.20   $207.20   $207.20  
  Purchase #3 $22.72   8.513%   $24.6542   $24.65   $24.65   $24.70  
  Purchase #4 $231.45   7.173%   $248.0519   $248.05   $248.05   $248.10  
  Purchase #5 $19.73   8.748%   $21.456   $21.46   $21.45   $21.50  
  Purchase #6 $59.81   4.654%   $62.5936   $62.59   $62.60   $62.60  
  Purchase #7 $89.98   11.334%   $100.1783   $100.18   $100.20   $100.20  
  7 purchase totals = $700.90       $765.3035   $765.30   $765.30   $765.50