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 $92.28   3.164%   $95.1997   $95.20   $95.20   $95.20  
  Purchase #2 $145.77   8.176%   $157.6882   $157.69   $157.70   $157.70  
  Purchase #3 $15.98   12.158%   $17.9228   $17.92   $17.90   $17.90  
  Purchase #4 $188.90   8.823%   $205.5666   $205.57   $205.55   $205.60  
  Purchase #5 $54.90   7.621%   $59.0839   $59.08   $59.10   $59.10  
  Purchase #6 $233.92   4.751%   $245.0335   $245.03   $245.05   $245.00  
  Purchase #7 $185.95   11.753%   $207.8047   $207.80   $207.80   $207.80  
  7 purchase totals = $917.70       $988.2994   $988.29   $988.30   $988.30