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	$228.61	11.816%	$255.6226	$255.62	$255.60	$255.60
Purchase #2	$46.69	3.302%	$48.2317	$48.23	$48.25	$48.20
Purchase #3	$178.27	3.275%	$184.1083	$184.11	$184.10	$184.10
Purchase #4	$114.76	10.371%	$126.6618	$126.66	$126.65	$126.70
Purchase #5	$145.83	12.644%	$164.2687	$164.27	$164.25	$164.30
Purchase #6	$153.54	11.233%	$170.7871	$170.79	$170.80	$170.80
Purchase #7	$141.26	6.476%	$150.408	$150.41	$150.40	$150.40
7 purchase totals =	$1,008.96		$1,100.0882	$1,100.09	$1,100.05	$1,100.10