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	$193.41	9.521%	$211.8246	$211.82	$211.80	$211.80
Purchase #2	$213.88	6.785%	$228.3918	$228.39	$228.40	$228.40
Purchase #3	$217.86	12.766%	$245.672	$245.67	$245.65	$245.70
Purchase #4	$34.52	10.201%	$38.0414	$38.04	$38.05	$38.00
Purchase #5	$88.61	12.696%	$99.8599	$99.86	$99.85	$99.90
Purchase #6	$49.58	9.777%	$54.4274	$54.43	$54.45	$54.40
Purchase #7	$54.67	10.123%	$60.2042	$60.20	$60.20	$60.20
7 purchase totals =	$852.53		$938.4213	$938.41	$938.40	$938.40