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	$68.97	5.201%	$72.5571	$72.56	$72.55	$72.60
Purchase #2	$203.46	13.532%	$230.9922	$230.99	$231.00	$231.00
Purchase #3	$87.72	11.258%	$97.5955	$97.60	$97.60	$97.60
Purchase #4	$55.54	10.120%	$61.1606	$61.16	$61.15	$61.20
Purchase #5	$201.31	10.733%	$222.9166	$222.92	$222.90	$222.90
Purchase #6	$25.76	11.145%	$28.631	$28.63	$28.65	$28.60
Purchase #7	$55.96	12.108%	$62.7356	$62.74	$62.75	$62.70
7 purchase totals =	$698.72		$776.5886	$776.60	$776.60	$776.60