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	$54.43	9.411%	$59.5524	$59.55	$59.55	$59.60
Purchase #2	$168.49	4.254%	$175.6576	$175.66	$175.65	$175.70
Purchase #3	$101.27	4.109%	$105.4312	$105.43	$105.45	$105.40
Purchase #4	$146.59	13.716%	$166.6963	$166.70	$166.70	$166.70
Purchase #5	$40.91	5.559%	$43.1842	$43.18	$43.20	$43.20
Purchase #6	$149.61	12.503%	$168.3157	$168.32	$168.30	$168.30
Purchase #7	$89.76	4.653%	$93.9365	$93.94	$93.95	$93.90
7 purchase totals =	$751.06		$812.7739	$812.78	$812.80	$812.80