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	$14.39	5.277%	$15.1494	$15.15	$15.15	$15.10
Purchase #2	$102.76	11.582%	$114.6617	$114.66	$114.65	$114.70
Purchase #3	$33.69	10.449%	$37.2103	$37.21	$37.20	$37.20
Purchase #4	$207.67	3.817%	$215.5968	$215.60	$215.60	$215.60
Purchase #5	$242.60	5.177%	$255.1594	$255.16	$255.15	$255.20
Purchase #6	$224.71	10.120%	$247.4507	$247.45	$247.45	$247.50
Purchase #7	$106.37	13.273%	$120.4885	$120.49	$120.50	$120.50
7 purchase totals =	$932.19		$1,005.7168	$1,005.72	$1,005.70	$1,005.80