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	$68.96	9.678%	$75.6339	$75.63	$75.65	$75.60
Purchase #2	$42.27	8.528%	$45.8748	$45.87	$45.85	$45.90
Purchase #3	$236.89	13.748%	$269.4576	$269.46	$269.45	$269.50
Purchase #4	$69.80	9.517%	$76.4429	$76.44	$76.45	$76.40
Purchase #5	$196.28	4.454%	$205.0223	$205.02	$205.00	$205.00
Purchase #6	$99.32	12.624%	$111.8582	$111.86	$111.85	$111.90
Purchase #7	$83.66	4.518%	$87.4398	$87.44	$87.45	$87.40
7 purchase totals =	$797.18		$871.7295	$871.72	$871.70	$871.70