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	$248.81	13.866%	$283.31	$283.31	$283.30	$283.30
Purchase #2	$157.90	13.817%	$179.717	$179.72	$179.70	$179.70
Purchase #3	$226.59	10.148%	$249.5844	$249.58	$249.60	$249.60
Purchase #4	$228.49	12.331%	$256.6651	$256.67	$256.65	$256.70
Purchase #5	$214.73	8.170%	$232.2734	$232.27	$232.25	$232.30
Purchase #6	$40.75	4.142%	$42.4379	$42.44	$42.45	$42.40
Purchase #7	$228.50	12.290%	$256.5827	$256.58	$256.60	$256.60
7 purchase totals =	$1,345.77		$1,500.5705	$1,500.57	$1,500.55	$1,500.60