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	$233.50	9.505%	$255.6942	$255.69	$255.70	$255.70
Purchase #2	$19.82	5.141%	$20.8389	$20.84	$20.85	$20.80
Purchase #3	$246.26	7.269%	$264.1606	$264.16	$264.15	$264.20
Purchase #4	$37.47	12.435%	$42.1294	$42.13	$42.15	$42.10
Purchase #5	$236.82	8.613%	$257.2173	$257.22	$257.20	$257.20
Purchase #6	$38.53	9.308%	$42.1164	$42.12	$42.10	$42.10
Purchase #7	$81.63	4.161%	$85.0266	$85.03	$85.05	$85.00
7 purchase totals =	$894.03		$967.1834	$967.19	$967.20	$967.10