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	$36.29	4.485%	$37.9176	$37.92	$37.90	$37.90
Purchase #2	$132.80	9.396%	$145.2779	$145.28	$145.30	$145.30
Purchase #3	$72.50	10.809%	$80.3365	$80.34	$80.35	$80.30
Purchase #4	$126.51	8.628%	$137.4253	$137.43	$137.45	$137.40
Purchase #5	$60.32	12.328%	$67.7562	$67.76	$67.75	$67.80
Purchase #6	$111.58	13.824%	$127.0048	$127.00	$127.00	$127.00
Purchase #7	$100.73	5.370%	$106.1392	$106.14	$106.15	$106.10
7 purchase totals =	$640.73		$701.8575	$701.87	$701.90	$701.80