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	$140.29	7.843%	$151.2929	$151.29	$151.30	$151.30
Purchase #2	$31.56	12.186%	$35.4059	$35.41	$35.40	$35.40
Purchase #3	$59.48	8.531%	$64.5542	$64.55	$64.55	$64.60
Purchase #4	$91.91	9.362%	$100.5146	$100.51	$100.50	$100.50
Purchase #5	$132.65	12.183%	$148.8107	$148.81	$148.80	$148.80
Purchase #6	$242.36	5.662%	$256.0824	$256.08	$256.10	$256.10
Purchase #7	$213.55	4.143%	$222.3974	$222.40	$222.40	$222.40
7 purchase totals =	$911.80		$979.0581	$979.05	$979.05	$979.10