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 $184.57   6.115%   $195.8565   $195.86   $195.85   $195.90  
  Purchase #2 $70.74   4.592%   $73.9884   $73.99   $74.00   $74.00  
  Purchase #3 $172.71   5.138%   $181.5838   $181.58   $181.60   $181.60  
  Purchase #4 $206.34   10.447%   $227.8963   $227.90   $227.90   $227.90  
  Purchase #5 $184.67   11.306%   $205.5488   $205.55   $205.55   $205.50  
  Purchase #6 $197.82   9.864%   $217.333   $217.33   $217.35   $217.30  
  Purchase #7 $47.60   5.817%   $50.3689   $50.37   $50.35   $50.40  
  7 purchase totals = $1,064.45       $1,152.5757   $1,152.58   $1,152.60   $1,152.60