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	$223.67	4.561%	$233.8716	$233.87	$233.85	$233.90
Purchase #2	$165.73	13.479%	$188.0687	$188.07	$188.05	$188.10
Purchase #3	$86.59	5.171%	$91.0676	$91.07	$91.05	$91.10
Purchase #4	$14.69	11.725%	$16.4124	$16.41	$16.40	$16.40
Purchase #5	$18.89	10.278%	$20.8315	$20.83	$20.85	$20.80
Purchase #6	$235.63	11.271%	$262.1879	$262.19	$262.20	$262.20
Purchase #7	$56.26	5.176%	$59.172	$59.17	$59.15	$59.20
7 purchase totals =	$801.46		$871.6117	$871.61	$871.55	$871.70