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	$191.37	10.810%	$212.0571	$212.06	$212.05	$212.10
Purchase #2	$112.49	13.330%	$127.4849	$127.48	$127.50	$127.50
Purchase #3	$88.41	9.433%	$96.7497	$96.75	$96.75	$96.70
Purchase #4	$152.84	3.513%	$158.2093	$158.21	$158.20	$158.20
Purchase #5	$131.90	11.622%	$147.2294	$147.23	$147.25	$147.20
Purchase #6	$71.68	9.722%	$78.6487	$78.65	$78.65	$78.60
Purchase #7	$27.38	3.679%	$28.3873	$28.39	$28.40	$28.40
7 purchase totals =	$776.07		$848.7664	$848.77	$848.80	$848.70