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	$225.76	3.408%	$233.4539	$233.45	$233.45	$233.50
Purchase #2	$133.78	13.607%	$151.9834	$151.98	$152.00	$152.00
Purchase #3	$221.79	12.479%	$249.4672	$249.47	$249.45	$249.50
Purchase #4	$74.58	7.813%	$80.4069	$80.41	$80.40	$80.40
Purchase #5	$53.43	6.874%	$57.1028	$57.10	$57.10	$57.10
Purchase #6	$234.99	11.773%	$262.6554	$262.66	$262.65	$262.70
Purchase #7	$44.47	4.776%	$46.5939	$46.59	$46.60	$46.60
7 purchase totals =	$988.80		$1,081.6635	$1,081.66	$1,081.65	$1,081.80