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	$188.72	13.718%	$214.6086	$214.61	$214.60	$214.60
Purchase #2	$162.35	8.706%	$176.4842	$176.48	$176.50	$176.50
Purchase #3	$188.89	4.178%	$196.7818	$196.78	$196.80	$196.80
Purchase #4	$91.50	7.454%	$98.3204	$98.32	$98.30	$98.30
Purchase #5	$175.84	12.137%	$197.1817	$197.18	$197.20	$197.20
Purchase #6	$109.33	13.843%	$124.4646	$124.46	$124.45	$124.50
Purchase #7	$46.93	4.250%	$48.9245	$48.92	$48.90	$48.90
7 purchase totals =	$963.56		$1,056.7658	$1,056.75	$1,056.75	$1,056.80