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	$78.82	11.734%	$88.0687	$88.07	$88.05	$88.10
Purchase #2	$130.95	8.510%	$142.0938	$142.09	$142.10	$142.10
Purchase #3	$108.66	10.739%	$120.329	$120.33	$120.35	$120.30
Purchase #4	$156.68	5.731%	$165.6593	$165.66	$165.65	$165.70
Purchase #5	$59.27	12.173%	$66.4849	$66.48	$66.50	$66.50
Purchase #6	$83.35	6.165%	$88.4885	$88.49	$88.50	$88.50
Purchase #7	$79.64	12.461%	$89.5639	$89.56	$89.55	$89.60
7 purchase totals =	$697.37		$760.6881	$760.68	$760.70	$760.80