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	$151.67	10.522%	$167.6287	$167.63	$167.65	$167.60
Purchase #2	$135.65	12.241%	$152.2549	$152.25	$152.25	$152.30
Purchase #3	$62.58	4.771%	$65.5657	$65.57	$65.55	$65.60
Purchase #4	$91.39	10.260%	$100.7666	$100.77	$100.75	$100.80
Purchase #5	$125.27	13.310%	$141.9434	$141.94	$141.95	$141.90
Purchase #6	$113.76	11.634%	$126.9948	$126.99	$127.00	$127.00
Purchase #7	$91.45	3.351%	$94.5145	$94.51	$94.50	$94.50
7 purchase totals =	$771.77		$849.6686	$849.66	$849.65	$849.70