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	$117.32	12.543%	$132.0354	$132.04	$132.05	$132.00
Purchase #2	$179.82	9.390%	$196.7051	$196.71	$196.70	$196.70
Purchase #3	$106.41	8.840%	$115.8166	$115.82	$115.80	$115.80
Purchase #4	$140.84	7.415%	$151.2833	$151.28	$151.30	$151.30
Purchase #5	$57.38	11.760%	$64.1279	$64.13	$64.15	$64.10
Purchase #6	$184.47	6.414%	$196.3019	$196.30	$196.30	$196.30
Purchase #7	$52.73	6.504%	$56.1596	$56.16	$56.15	$56.20
7 purchase totals =	$838.97		$912.4298	$912.44	$912.45	$912.40