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 $221.52   5.852%   $234.4834   $234.48   $234.50   $234.50  
  Purchase #2 $115.67   8.593%   $125.6095   $125.61   $125.60   $125.60  
  Purchase #3 $156.91   13.541%   $178.1572   $178.16   $178.15   $178.20  
  Purchase #4 $198.26   3.582%   $205.3617   $205.36   $205.35   $205.40  
  Purchase #5 $215.30   9.751%   $236.2939   $236.29   $236.30   $236.30  
  Purchase #6 $152.49   5.538%   $160.9349   $160.93   $160.95   $160.90  
  Purchase #7 $193.95   3.456%   $200.6529   $200.65   $200.65   $200.70  
  7 purchase totals = $1,254.10       $1,341.4935   $1,341.48   $1,341.50   $1,341.60