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 $95.50   3.514%   $98.8559   $98.86   $98.85   $98.90  
  Purchase #2 $223.85   4.685%   $234.3374   $234.34   $234.35   $234.30  
  Purchase #3 $240.55   9.533%   $263.4816   $263.48   $263.50   $263.50  
  Purchase #4 $86.33   6.268%   $91.7412   $91.74   $91.75   $91.70  
  Purchase #5 $166.53   6.265%   $176.9631   $176.96   $176.95   $177.00  
  Purchase #6 $234.46   4.283%   $244.5019   $244.50   $244.50   $244.50  
  Purchase #7 $200.59   5.873%   $212.3707   $212.37   $212.35   $212.40  
  7 purchase totals = $1,247.81       $1,322.2518   $1,322.25   $1,322.25   $1,322.30