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	$7.96	4.605%	$8.3266	$8.33	$8.35	$8.30
Purchase #2	$105.26	13.205%	$119.1596	$119.16	$119.15	$119.20
Purchase #3	$144.96	11.247%	$161.2637	$161.26	$161.25	$161.30
Purchase #4	$79.41	11.201%	$88.3047	$88.30	$88.30	$88.30
Purchase #5	$59.28	13.767%	$67.4411	$67.44	$67.45	$67.40
Purchase #6	$54.78	8.717%	$59.5552	$59.56	$59.55	$59.60
Purchase #7	$181.61	10.453%	$200.5937	$200.59	$200.60	$200.60
7 purchase totals =	$633.26		$704.6446	$704.64	$704.65	$704.70