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	$146.62	9.270%	$160.2117	$160.21	$160.20	$160.20
Purchase #2	$88.55	9.617%	$97.0659	$97.07	$97.05	$97.10
Purchase #3	$129.95	10.384%	$143.444	$143.44	$143.45	$143.40
Purchase #4	$211.46	5.391%	$222.8598	$222.86	$222.85	$222.90
Purchase #5	$106.37	4.720%	$111.3907	$111.39	$111.40	$111.40
Purchase #6	$228.50	5.530%	$241.1361	$241.14	$241.15	$241.10
Purchase #7	$220.85	13.405%	$250.4549	$250.45	$250.45	$250.50
7 purchase totals =	$1,132.30		$1,226.5631	$1,226.56	$1,226.55	$1,226.60