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	$160.43	13.592%	$182.2356	$182.24	$182.25	$182.20
Purchase #2	$30.29	11.793%	$33.8621	$33.86	$33.85	$33.90
Purchase #3	$137.74	5.164%	$144.8529	$144.85	$144.85	$144.90
Purchase #4	$223.82	13.779%	$254.6602	$254.66	$254.65	$254.70
Purchase #5	$69.62	13.318%	$78.892	$78.89	$78.90	$78.90
Purchase #6	$57.35	10.346%	$63.2834	$63.28	$63.30	$63.30
Purchase #7	$62.61	5.584%	$66.1061	$66.11	$66.10	$66.10
7 purchase totals =	$741.86		$823.8923	$823.89	$823.90	$824.00