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	$217.83	9.292%	$238.0708	$238.07	$238.05	$238.10
Purchase #2	$181.76	4.723%	$190.3445	$190.34	$190.35	$190.30
Purchase #3	$135.67	11.740%	$151.5977	$151.60	$151.60	$151.60
Purchase #4	$233.55	7.368%	$250.758	$250.76	$250.75	$250.80
Purchase #5	$27.54	3.500%	$28.5039	$28.50	$28.50	$28.50
Purchase #6	$129.42	3.672%	$134.1723	$134.17	$134.15	$134.20
Purchase #7	$240.26	6.859%	$256.7394	$256.74	$256.75	$256.70
7 purchase totals =	$1,166.03		$1,250.1866	$1,250.18	$1,250.15	$1,250.20