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 $43.27   3.328%   $44.71   $44.71   $44.70   $44.70  
  Purchase #2 $150.44   13.634%   $170.951   $170.95   $170.95   $171.00  
  Purchase #3 $176.89   10.253%   $195.0265   $195.03   $195.05   $195.00  
  Purchase #4 $202.37   4.356%   $211.1852   $211.19   $211.20   $211.20  
  Purchase #5 $182.35   12.742%   $205.585   $205.59   $205.60   $205.60  
  Purchase #6 $176.73   4.633%   $184.9179   $184.92   $184.90   $184.90  
  Purchase #7 $86.51   8.775%   $94.1013   $94.10   $94.10   $94.10  
  7 purchase totals = $1,018.56       $1,106.4769   $1,106.49   $1,106.50   $1,106.50