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	$158.30	4.397%	$165.2605	$165.26	$165.25	$165.30
Purchase #2	$182.74	7.551%	$196.5387	$196.54	$196.55	$196.50
Purchase #3	$239.99	6.282%	$255.0662	$255.07	$255.05	$255.10
Purchase #4	$61.85	9.310%	$67.6082	$67.61	$67.60	$67.60
Purchase #5	$229.59	11.830%	$256.7505	$256.75	$256.75	$256.80
Purchase #6	$229.29	6.301%	$243.7376	$243.74	$243.75	$243.70
Purchase #7	$171.64	7.798%	$185.0245	$185.02	$185.00	$185.00
7 purchase totals =	$1,273.40		$1,369.9862	$1,369.99	$1,369.95	$1,370.00