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	$161.28	8.577%	$175.113	$175.11	$175.10	$175.10
Purchase #2	$168.95	11.150%	$187.7879	$187.79	$187.80	$187.80
Purchase #3	$146.27	13.549%	$166.0881	$166.09	$166.10	$166.10
Purchase #4	$113.46	12.133%	$127.2261	$127.23	$127.25	$127.20
Purchase #5	$224.73	13.812%	$255.7697	$255.77	$255.75	$255.80
Purchase #6	$165.66	12.108%	$185.7181	$185.72	$185.70	$185.70
Purchase #7	$64.44	6.819%	$68.8342	$68.83	$68.85	$68.80
7 purchase totals =	$1,044.79		$1,166.5371	$1,166.54	$1,166.55	$1,166.50