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 $76.51   12.333%   $85.946   $85.95   $85.95   $85.90  
  Purchase #2 $233.72   4.514%   $244.2701   $244.27   $244.25   $244.30  
  Purchase #3 $199.56   3.172%   $205.89   $205.89   $205.90   $205.90  
  Purchase #4 $155.25   9.633%   $170.2052   $170.21   $170.20   $170.20  
  Purchase #5 $49.55   11.656%   $55.3255   $55.33   $55.35   $55.30  
  Purchase #6 $138.66   12.199%   $155.5751   $155.58   $155.60   $155.60  
  Purchase #7 $109.80   13.603%   $124.7361   $124.74   $124.75   $124.70  
  7 purchase totals = $963.05       $1,041.9480   $1,041.97   $1,042.00   $1,041.90