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	$143.30	8.395%	$155.33	$155.33	$155.35	$155.30
Purchase #2	$69.39	6.403%	$73.833	$73.83	$73.85	$73.80
Purchase #3	$131.39	11.335%	$146.2831	$146.28	$146.30	$146.30
Purchase #4	$196.37	10.746%	$217.4719	$217.47	$217.45	$217.50
Purchase #5	$91.86	12.161%	$103.0311	$103.03	$103.05	$103.00
Purchase #6	$82.64	11.692%	$92.3023	$92.30	$92.30	$92.30
Purchase #7	$74.33	6.431%	$79.1102	$79.11	$79.10	$79.10
7 purchase totals =	$789.28		$867.3616	$867.35	$867.40	$867.30