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	$143.62	6.200%	$152.5244	$152.52	$152.50	$152.50
Purchase #2	$125.66	11.605%	$140.2428	$140.24	$140.25	$140.20
Purchase #3	$36.69	9.527%	$40.1855	$40.19	$40.20	$40.20
Purchase #4	$237.83	11.152%	$264.3528	$264.35	$264.35	$264.40
Purchase #5	$45.76	7.388%	$49.1407	$49.14	$49.15	$49.10
Purchase #6	$146.65	12.120%	$164.424	$164.42	$164.40	$164.40
Purchase #7	$127.77	11.173%	$142.0457	$142.05	$142.05	$142.00
7 purchase totals =	$863.98		$952.9159	$952.91	$952.90	$952.80