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	$43.32	5.658%	$45.771	$45.77	$45.75	$45.80
Purchase #2	$228.26	7.140%	$244.5578	$244.56	$244.55	$244.60
Purchase #3	$152.78	9.476%	$167.2574	$167.26	$167.25	$167.30
Purchase #4	$166.56	7.534%	$179.1086	$179.11	$179.10	$179.10
Purchase #5	$166.35	7.858%	$179.4218	$179.42	$179.40	$179.40
Purchase #6	$109.80	8.293%	$118.9057	$118.91	$118.90	$118.90
Purchase #7	$137.71	11.115%	$153.0165	$153.02	$153.00	$153.00
7 purchase totals =	$1,004.78		$1,088.0388	$1,088.05	$1,087.95	$1,088.10