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	$89.27	7.251%	$95.743	$95.74	$95.75	$95.70
Purchase #2	$135.80	4.335%	$141.6869	$141.69	$141.70	$141.70
Purchase #3	$69.47	4.721%	$72.7497	$72.75	$72.75	$72.70
Purchase #4	$115.28	12.686%	$129.9044	$129.90	$129.90	$129.90
Purchase #5	$182.70	3.186%	$188.5208	$188.52	$188.50	$188.50
Purchase #6	$72.37	8.735%	$78.6915	$78.69	$78.70	$78.70
Purchase #7	$139.86	13.354%	$158.5369	$158.54	$158.55	$158.50
7 purchase totals =	$804.75		$865.8332	$865.83	$865.85	$865.70