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	$235.98	13.343%	$267.4668	$267.47	$267.45	$267.50
Purchase #2	$35.39	6.112%	$37.553	$37.55	$37.55	$37.60
Purchase #3	$243.30	5.239%	$256.0465	$256.05	$256.05	$256.00
Purchase #4	$53.83	4.487%	$56.2454	$56.25	$56.25	$56.20
Purchase #5	$123.77	5.736%	$130.8694	$130.87	$130.85	$130.90
Purchase #6	$60.49	12.847%	$68.2612	$68.26	$68.25	$68.30
Purchase #7	$17.44	5.769%	$18.4461	$18.45	$18.45	$18.40
7 purchase totals =	$770.20		$834.8884	$834.90	$834.85	$834.90