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	$49.48	9.853%	$54.3553	$54.36	$54.35	$54.40
Purchase #2	$117.35	8.550%	$127.3834	$127.38	$127.40	$127.40
Purchase #3	$80.87	3.595%	$83.7773	$83.78	$83.80	$83.80
Purchase #4	$131.97	11.168%	$146.7084	$146.71	$146.70	$146.70
Purchase #5	$111.28	4.349%	$116.1196	$116.12	$116.10	$116.10
Purchase #6	$212.80	13.321%	$241.1471	$241.15	$241.15	$241.10
Purchase #7	$55.96	7.334%	$60.0641	$60.06	$60.05	$60.10
7 purchase totals =	$759.71		$829.5552	$829.56	$829.55	$829.60