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 $162.54   11.777%   $181.6823   $181.68   $181.70   $181.70  
  Purchase #2 $43.76   4.473%   $45.7174   $45.72   $45.70   $45.70  
  Purchase #3 $186.94   4.684%   $195.6963   $195.70   $195.70   $195.70  
  Purchase #4 $187.82   8.874%   $204.4871   $204.49   $204.50   $204.50  
  Purchase #5 $109.71   3.846%   $113.9294   $113.93   $113.95   $113.90  
  Purchase #6 $168.98   7.145%   $181.0536   $181.05   $181.05   $181.10  
  Purchase #7 $88.86   5.306%   $93.5749   $93.57   $93.55   $93.60  
  7 purchase totals = $948.61       $1,016.1410   $1,016.14   $1,016.15   $1,016.20