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	$76.68	13.350%	$86.9168	$86.92	$86.90	$86.90
Purchase #2	$217.48	6.351%	$231.2922	$231.29	$231.30	$231.30
Purchase #3	$101.38	10.222%	$111.7431	$111.74	$111.75	$111.70
Purchase #4	$92.64	8.713%	$100.7117	$100.71	$100.70	$100.70
Purchase #5	$127.63	8.562%	$138.5577	$138.56	$138.55	$138.60
Purchase #6	$249.33	8.200%	$269.7751	$269.78	$269.80	$269.80
Purchase #7	$223.61	5.465%	$235.8303	$235.83	$235.85	$235.80
7 purchase totals =	$1,088.75		$1,174.8269	$1,174.83	$1,174.85	$1,174.80