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	$148.30	6.831%	$158.4304	$158.43	$158.45	$158.40
Purchase #2	$64.90	7.130%	$69.5274	$69.53	$69.55	$69.50
Purchase #3	$96.44	9.425%	$105.5295	$105.53	$105.55	$105.50
Purchase #4	$35.74	4.138%	$37.2189	$37.22	$37.20	$37.20
Purchase #5	$229.40	5.693%	$242.4597	$242.46	$242.45	$242.50
Purchase #6	$130.34	6.321%	$138.5788	$138.58	$138.60	$138.60
Purchase #7	$127.33	4.532%	$133.1006	$133.10	$133.10	$133.10
7 purchase totals =	$832.45		$884.8453	$884.85	$884.90	$884.80