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	$236.93	5.759%	$250.5748	$250.57	$250.55	$250.60
Purchase #2	$175.32	11.503%	$195.4871	$195.49	$195.50	$195.50
Purchase #3	$196.69	6.715%	$209.8977	$209.90	$209.90	$209.90
Purchase #4	$248.74	11.871%	$278.2679	$278.27	$278.25	$278.30
Purchase #5	$33.86	4.265%	$35.3041	$35.30	$35.30	$35.30
Purchase #6	$105.61	3.142%	$108.9283	$108.93	$108.95	$108.90
Purchase #7	$107.75	9.679%	$118.1791	$118.18	$118.20	$118.20
7 purchase totals =	$1,104.90		$1,196.6390	$1,196.64	$1,196.65	$1,196.70