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	$58.73	11.605%	$65.5456	$65.55	$65.55	$65.50
Purchase #2	$127.82	11.306%	$142.2713	$142.27	$142.25	$142.30
Purchase #3	$33.87	13.355%	$38.3933	$38.39	$38.40	$38.40
Purchase #4	$229.57	9.559%	$251.5146	$251.51	$251.50	$251.50
Purchase #5	$87.42	4.359%	$91.2306	$91.23	$91.25	$91.20
Purchase #6	$250.50	11.368%	$278.9768	$278.98	$279.00	$279.00
Purchase #7	$67.53	10.648%	$74.7206	$74.72	$74.70	$74.70
7 purchase totals =	$855.44		$942.6528	$942.65	$942.65	$942.60