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	$59.73	3.519%	$61.8319	$61.83	$61.85	$61.80
Purchase #2	$108.99	12.430%	$122.5375	$122.54	$122.55	$122.50
Purchase #3	$116.94	10.643%	$129.3859	$129.39	$129.40	$129.40
Purchase #4	$156.36	5.316%	$164.6721	$164.67	$164.65	$164.70
Purchase #5	$244.63	4.440%	$255.4916	$255.49	$255.50	$255.50
Purchase #6	$110.92	6.672%	$118.3206	$118.32	$118.30	$118.30
Purchase #7	$28.34	13.789%	$32.2478	$32.25	$32.25	$32.20
7 purchase totals =	$825.91		$884.4874	$884.49	$884.50	$884.40