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	$145.92	4.418%	$152.3667	$152.37	$152.35	$152.40
Purchase #2	$90.42	11.121%	$100.4756	$100.48	$100.50	$100.50
Purchase #3	$48.60	12.327%	$54.5909	$54.59	$54.60	$54.60
Purchase #4	$218.45	5.702%	$230.906	$230.91	$230.90	$230.90
Purchase #5	$84.36	4.564%	$88.2102	$88.21	$88.20	$88.20
Purchase #6	$59.80	10.203%	$65.9014	$65.90	$65.90	$65.90
Purchase #7	$36.86	8.840%	$40.1184	$40.12	$40.10	$40.10
7 purchase totals =	$684.41		$732.5692	$732.58	$732.55	$732.60