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	$167.68	13.388%	$190.129	$190.13	$190.15	$190.10
Purchase #2	$104.45	11.459%	$116.4189	$116.42	$116.40	$116.40
Purchase #3	$144.63	9.468%	$158.3236	$158.32	$158.30	$158.30
Purchase #4	$91.57	8.432%	$99.2912	$99.29	$99.30	$99.30
Purchase #5	$46.91	12.658%	$52.8479	$52.85	$52.85	$52.80
Purchase #6	$61.30	13.800%	$69.7594	$69.76	$69.75	$69.80
Purchase #7	$197.88	9.607%	$216.8903	$216.89	$216.90	$216.90
7 purchase totals =	$814.42		$903.6603	$903.66	$903.65	$903.60