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	$130.52	7.594%	$140.4317	$140.43	$140.45	$140.40
Purchase #2	$205.32	10.129%	$226.1169	$226.12	$226.10	$226.10
Purchase #3	$80.37	7.780%	$86.6228	$86.62	$86.60	$86.60
Purchase #4	$37.47	13.240%	$42.431	$42.43	$42.45	$42.40
Purchase #5	$6.71	6.599%	$7.1528	$7.15	$7.15	$7.20
Purchase #6	$13.39	10.307%	$14.7701	$14.77	$14.75	$14.80
Purchase #7	$180.56	8.793%	$196.4366	$196.44	$196.45	$196.40
7 purchase totals =	$654.34		$713.9619	$713.96	$713.95	$713.90