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	$88.37	4.205%	$92.086	$92.09	$92.10	$92.10
Purchase #2	$16.88	10.314%	$18.621	$18.62	$18.60	$18.60
Purchase #3	$97.48	3.379%	$100.7738	$100.77	$100.75	$100.80
Purchase #4	$82.94	12.727%	$93.4958	$93.50	$93.50	$93.50
Purchase #5	$80.42	4.210%	$83.8057	$83.81	$83.80	$83.80
Purchase #6	$80.65	9.521%	$88.3287	$88.33	$88.35	$88.30
Purchase #7	$129.90	12.515%	$146.157	$146.16	$146.15	$146.20
7 purchase totals =	$576.64		$623.2680	$623.28	$623.25	$623.30