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 $142.61   7.237%   $152.9307   $152.93   $152.95   $152.90  
  Purchase #2 $212.77   11.262%   $236.7322   $236.73   $236.75   $236.70  
  Purchase #3 $62.44   7.531%   $67.1424   $67.14   $67.15   $67.10  
  Purchase #4 $232.58   12.800%   $262.3502   $262.35   $262.35   $262.40  
  Purchase #5 $203.29   5.374%   $214.2148   $214.21   $214.20   $214.20  
  Purchase #6 $30.89   4.589%   $32.3075   $32.31   $32.30   $32.30  
  Purchase #7 $42.94   3.627%   $44.4974   $44.50   $44.50   $44.50  
  7 purchase totals = $927.52       $1,010.1752   $1,010.17   $1,010.20   $1,010.10