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	$212.48	10.782%	$235.3896	$235.39	$235.40	$235.40
Purchase #2	$71.55	7.642%	$77.0179	$77.02	$77.00	$77.00
Purchase #3	$197.72	3.599%	$204.8359	$204.84	$204.85	$204.80
Purchase #4	$243.75	8.422%	$264.2786	$264.28	$264.30	$264.30
Purchase #5	$152.28	13.293%	$172.5226	$172.52	$172.50	$172.50
Purchase #6	$141.35	7.143%	$151.4466	$151.45	$151.45	$151.40
Purchase #7	$79.48	3.338%	$82.133	$82.13	$82.15	$82.10
7 purchase totals =	$1,098.61		$1,187.6242	$1,187.63	$1,187.65	$1,187.50