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	$171.67	6.510%	$182.8457	$182.85	$182.85	$182.80
Purchase #2	$105.90	11.472%	$118.0488	$118.05	$118.05	$118.00
Purchase #3	$127.42	5.778%	$134.7823	$134.78	$134.80	$134.80
Purchase #4	$80.97	12.741%	$91.2864	$91.29	$91.30	$91.30
Purchase #5	$95.33	4.804%	$99.9097	$99.91	$99.90	$99.90
Purchase #6	$213.38	8.208%	$230.8942	$230.89	$230.90	$230.90
Purchase #7	$18.40	5.149%	$19.3474	$19.35	$19.35	$19.30
7 purchase totals =	$813.07		$877.1145	$877.12	$877.15	$877.00