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	$72.86	6.620%	$77.6833	$77.68	$77.70	$77.70
Purchase #2	$101.32	9.632%	$111.0791	$111.08	$111.10	$111.10
Purchase #3	$205.64	6.634%	$219.2822	$219.28	$219.30	$219.30
Purchase #4	$248.38	9.217%	$271.2732	$271.27	$271.25	$271.30
Purchase #5	$58.73	10.843%	$65.0981	$65.10	$65.10	$65.10
Purchase #6	$101.65	11.818%	$113.663	$113.66	$113.65	$113.70
Purchase #7	$40.58	5.170%	$42.678	$42.68	$42.70	$42.70
7 purchase totals =	$829.16		$900.7569	$900.75	$900.80	$900.90