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	$226.48	7.662%	$243.8329	$243.83	$243.85	$243.80
Purchase #2	$33.66	4.781%	$35.2693	$35.27	$35.25	$35.30
Purchase #3	$166.86	11.172%	$185.5016	$185.50	$185.50	$185.50
Purchase #4	$109.73	6.567%	$116.936	$116.94	$116.95	$116.90
Purchase #5	$49.48	11.399%	$55.1202	$55.12	$55.10	$55.10
Purchase #6	$209.34	9.114%	$228.4192	$228.42	$228.40	$228.40
Purchase #7	$89.80	5.328%	$94.5845	$94.58	$94.60	$94.60
7 purchase totals =	$885.35		$959.6637	$959.66	$959.65	$959.60