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	$81.72	4.588%	$85.4693	$85.47	$85.45	$85.50
Purchase #2	$136.56	5.358%	$143.8769	$143.88	$143.90	$143.90
Purchase #3	$175.38	13.512%	$199.0773	$199.08	$199.10	$199.10
Purchase #4	$49.71	11.394%	$55.374	$55.37	$55.35	$55.40
Purchase #5	$159.91	13.574%	$181.6162	$181.62	$181.60	$181.60
Purchase #6	$234.80	12.764%	$264.7699	$264.77	$264.75	$264.80
Purchase #7	$195.26	9.610%	$214.0245	$214.02	$214.00	$214.00
7 purchase totals =	$1,033.34		$1,144.2081	$1,144.21	$1,144.15	$1,144.30