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 $88.49   7.332%   $94.9781   $94.98   $95.00   $95.00  
  Purchase #2 $237.97   6.687%   $253.8831   $253.88   $253.90   $253.90  
  Purchase #3 $129.62   13.790%   $147.4946   $147.49   $147.50   $147.50  
  Purchase #4 $168.29   12.703%   $189.6679   $189.67   $189.65   $189.70  
  Purchase #5 $138.68   11.561%   $154.7128   $154.71   $154.70   $154.70  
  Purchase #6 $150.30   6.259%   $159.7073   $159.71   $159.70   $159.70  
  Purchase #7 $228.75   5.119%   $240.4597   $240.46   $240.45   $240.50  
  7 purchase totals = $1,142.10       $1,240.9035   $1,240.90   $1,240.90   $1,241.00