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 $201.46   7.227%   $216.0195   $216.02   $216.00   $216.00  
  Purchase #2 $84.84   4.244%   $88.4406   $88.44   $88.45   $88.40  
  Purchase #3 $74.60   11.664%   $83.3013   $83.30   $83.30   $83.30  
  Purchase #4 $124.47   6.310%   $132.3241   $132.32   $132.30   $132.30  
  Purchase #5 $139.77   4.355%   $145.857   $145.86   $145.85   $145.90  
  Purchase #6 $187.48   9.216%   $204.7582   $204.76   $204.75   $204.80  
  Purchase #7 $182.59   7.681%   $196.6147   $196.61   $196.60   $196.60  
  7 purchase totals = $995.21       $1,067.3154   $1,067.31   $1,067.25   $1,067.30