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 $214.52   10.459%   $236.9566   $236.96   $236.95   $237.00  
  Purchase #2 $93.84   3.165%   $96.81   $96.81   $96.80   $96.80  
  Purchase #3 $56.60   9.333%   $61.8825   $61.88   $61.90   $61.90  
  Purchase #4 $223.86   13.380%   $253.8125   $253.81   $253.80   $253.80  
  Purchase #5 $133.75   6.576%   $142.5454   $142.55   $142.55   $142.50  
  Purchase #6 $84.34   12.414%   $94.81   $94.81   $94.80   $94.80  
  Purchase #7 $230.90   6.281%   $245.4028   $245.40   $245.40   $245.40  
  7 purchase totals = $1,037.81       $1,132.2198   $1,132.22   $1,132.20   $1,132.20