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	$128.35	4.613%	$134.2708	$134.27	$134.25	$134.30
Purchase #2	$35.99	3.213%	$37.1464	$37.15	$37.15	$37.10
Purchase #3	$222.65	10.662%	$246.3889	$246.39	$246.40	$246.40
Purchase #4	$227.28	11.480%	$253.3717	$253.37	$253.35	$253.40
Purchase #5	$38.87	4.693%	$40.6942	$40.69	$40.70	$40.70
Purchase #6	$19.63	4.438%	$20.5012	$20.50	$20.50	$20.50
Purchase #7	$236.77	13.772%	$269.378	$269.38	$269.40	$269.40
7 purchase totals =	$909.54		$1,001.7512	$1,001.75	$1,001.75	$1,001.80