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 $66.42   11.426%   $74.0091   $74.01   $74.00   $74.00  
  Purchase #2 $229.43   10.495%   $253.5087   $253.51   $253.50   $253.50  
  Purchase #3 $86.61   6.472%   $92.2154   $92.22   $92.20   $92.20  
  Purchase #4 $61.82   9.288%   $67.5618   $67.56   $67.55   $67.60  
  Purchase #5 $178.60   12.459%   $200.8518   $200.85   $200.85   $200.90  
  Purchase #6 $196.47   9.169%   $214.4843   $214.48   $214.50   $214.50  
  Purchase #7 $245.97   4.633%   $257.3658   $257.37   $257.35   $257.40  
  7 purchase totals = $1,065.32       $1,159.9969   $1,160.00   $1,159.95   $1,160.10