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	$59.80	3.367%	$61.8135	$61.81	$61.80	$61.80
Purchase #2	$61.63	6.224%	$65.4659	$65.47	$65.45	$65.50
Purchase #3	$56.37	6.239%	$59.8869	$59.89	$59.90	$59.90
Purchase #4	$83.65	3.186%	$86.3151	$86.32	$86.30	$86.30
Purchase #5	$99.69	4.445%	$104.1212	$104.12	$104.10	$104.10
Purchase #6	$41.70	5.300%	$43.9101	$43.91	$43.90	$43.90
Purchase #7	$168.85	4.603%	$176.6222	$176.62	$176.60	$176.60
7 purchase totals =	$571.69		$598.1349	$598.14	$598.05	$598.10