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	$179.29	11.243%	$199.4476	$199.45	$199.45	$199.40
Purchase #2	$248.88	11.258%	$276.8989	$276.90	$276.90	$276.90
Purchase #3	$27.96	6.804%	$29.8624	$29.86	$29.85	$29.90
Purchase #4	$105.35	4.761%	$110.3657	$110.37	$110.35	$110.40
Purchase #5	$128.56	11.314%	$143.1053	$143.11	$143.10	$143.10
Purchase #6	$137.25	6.580%	$146.2811	$146.28	$146.30	$146.30
Purchase #7	$152.37	6.401%	$162.1232	$162.12	$162.10	$162.10
7 purchase totals =	$979.66		$1,068.0842	$1,068.09	$1,068.05	$1,068.10