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	$103.84	8.141%	$112.2936	$112.29	$112.30	$112.30
Purchase #2	$227.96	9.189%	$248.9072	$248.91	$248.90	$248.90
Purchase #3	$202.33	6.306%	$215.0889	$215.09	$215.10	$215.10
Purchase #4	$216.32	12.512%	$243.386	$243.39	$243.40	$243.40
Purchase #5	$101.73	3.730%	$105.5245	$105.52	$105.50	$105.50
Purchase #6	$22.41	13.795%	$25.5015	$25.50	$25.50	$25.50
Purchase #7	$102.71	5.819%	$108.6867	$108.69	$108.70	$108.70
7 purchase totals =	$977.30		$1,059.3884	$1,059.39	$1,059.40	$1,059.40