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	$92.71	4.109%	$96.5195	$96.52	$96.50	$96.50
Purchase #2	$36.78	12.336%	$41.3172	$41.32	$41.30	$41.30
Purchase #3	$28.65	12.764%	$32.3069	$32.31	$32.30	$32.30
Purchase #4	$153.69	3.184%	$158.5835	$158.58	$158.60	$158.60
Purchase #5	$73.50	6.425%	$78.2224	$78.22	$78.20	$78.20
Purchase #6	$234.87	10.438%	$259.3857	$259.39	$259.40	$259.40
Purchase #7	$58.85	3.779%	$61.0739	$61.07	$61.05	$61.10
7 purchase totals =	$679.05		$727.4091	$727.41	$727.35	$727.40