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	$180.63	7.249%	$193.7239	$193.72	$193.70	$193.70
Purchase #2	$109.51	3.689%	$113.5498	$113.55	$113.55	$113.50
Purchase #3	$30.88	6.308%	$32.8279	$32.83	$32.85	$32.80
Purchase #4	$127.52	5.389%	$134.3921	$134.39	$134.40	$134.40
Purchase #5	$98.86	4.707%	$103.5133	$103.51	$103.50	$103.50
Purchase #6	$157.75	10.132%	$173.7332	$173.73	$173.75	$173.70
Purchase #7	$114.77	7.635%	$123.5327	$123.53	$123.55	$123.50
7 purchase totals =	$819.92		$875.2729	$875.26	$875.30	$875.10