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	$195.53	4.350%	$204.0356	$204.04	$204.05	$204.00
Purchase #2	$81.84	9.584%	$89.6835	$89.68	$89.70	$89.70
Purchase #3	$236.95	13.856%	$269.7818	$269.78	$269.80	$269.80
Purchase #4	$126.33	5.407%	$133.1607	$133.16	$133.15	$133.20
Purchase #5	$211.91	7.584%	$227.9813	$227.98	$228.00	$228.00
Purchase #6	$216.38	11.196%	$240.6059	$240.61	$240.60	$240.60
Purchase #7	$83.36	8.295%	$90.2747	$90.27	$90.25	$90.30
7 purchase totals =	$1,152.30		$1,255.5235	$1,255.52	$1,255.55	$1,255.60