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 $84.71   12.103%   $94.9625   $94.96   $94.95   $95.00  
  Purchase #2 $244.70   11.352%   $272.4783   $272.48   $272.50   $272.50  
  Purchase #3 $242.60   4.320%   $253.0803   $253.08   $253.10   $253.10  
  Purchase #4 $43.84   9.572%   $48.0364   $48.04   $48.05   $48.00  
  Purchase #5 $197.80   9.240%   $216.0767   $216.08   $216.10   $216.10  
  Purchase #6 $113.47   7.863%   $122.3921   $122.39   $122.40   $122.40  
  Purchase #7 $89.94   4.582%   $94.0611   $94.06   $94.05   $94.10  
  7 purchase totals = $1,017.06       $1,101.0874   $1,101.09   $1,101.15   $1,101.20