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	$102.73	8.849%	$111.8206	$111.82	$111.80	$111.80
Purchase #2	$133.41	7.871%	$143.9107	$143.91	$143.90	$143.90
Purchase #3	$50.90	7.650%	$54.7939	$54.79	$54.80	$54.80
Purchase #4	$80.29	8.301%	$86.9549	$86.95	$86.95	$87.00
Purchase #5	$27.33	3.185%	$28.2005	$28.20	$28.20	$28.20
Purchase #6	$120.81	6.634%	$128.8245	$128.82	$128.80	$128.80
Purchase #7	$115.85	13.215%	$131.1596	$131.16	$131.15	$131.20
7 purchase totals =	$631.32		$685.6647	$685.65	$685.60	$685.70