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	$201.27	7.570%	$216.5061	$216.51	$216.50	$216.50
Purchase #2	$109.55	13.262%	$124.0785	$124.08	$124.10	$124.10
Purchase #3	$225.77	11.849%	$252.5215	$252.52	$252.50	$252.50
Purchase #4	$138.91	6.364%	$147.7502	$147.75	$147.75	$147.80
Purchase #5	$33.48	11.535%	$37.3419	$37.34	$37.35	$37.30
Purchase #6	$141.46	4.425%	$147.7196	$147.72	$147.70	$147.70
Purchase #7	$145.51	4.844%	$152.5585	$152.56	$152.55	$152.60
7 purchase totals =	$995.95		$1,078.4763	$1,078.48	$1,078.45	$1,078.50