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	$246.76	12.319%	$277.1584	$277.16	$277.15	$277.20
Purchase #2	$81.98	8.865%	$89.2475	$89.25	$89.25	$89.20
Purchase #3	$217.72	4.865%	$228.3121	$228.31	$228.30	$228.30
Purchase #4	$39.79	13.695%	$45.2392	$45.24	$45.25	$45.20
Purchase #5	$111.27	3.665%	$115.348	$115.35	$115.35	$115.30
Purchase #6	$92.92	5.624%	$98.1458	$98.15	$98.15	$98.10
Purchase #7	$103.81	5.130%	$109.1355	$109.14	$109.15	$109.10
7 purchase totals =	$894.25		$962.5865	$962.60	$962.60	$962.40