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	$231.65	12.183%	$259.8719	$259.87	$259.85	$259.90
Purchase #2	$80.51	3.421%	$83.2642	$83.26	$83.25	$83.30
Purchase #3	$188.77	10.367%	$208.3398	$208.34	$208.35	$208.30
Purchase #4	$151.56	5.838%	$160.4081	$160.41	$160.40	$160.40
Purchase #5	$218.82	5.640%	$231.1614	$231.16	$231.15	$231.20
Purchase #6	$242.83	4.496%	$253.7476	$253.75	$253.75	$253.70
Purchase #7	$56.92	4.197%	$59.3089	$59.31	$59.30	$59.30
7 purchase totals =	$1,171.06		$1,256.1019	$1,256.10	$1,256.05	$1,256.10