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	$200.61	11.420%	$223.5197	$223.52	$223.50	$223.50
Purchase #2	$85.56	10.323%	$94.3924	$94.39	$94.40	$94.40
Purchase #3	$211.59	5.131%	$222.4467	$222.45	$222.45	$222.40
Purchase #4	$171.26	6.339%	$182.1162	$182.12	$182.10	$182.10
Purchase #5	$214.49	11.390%	$238.9204	$238.92	$238.90	$238.90
Purchase #6	$223.73	4.786%	$234.4377	$234.44	$234.45	$234.40
Purchase #7	$202.74	4.701%	$212.2708	$212.27	$212.25	$212.30
7 purchase totals =	$1,309.98		$1,408.1039	$1,408.11	$1,408.05	$1,408.00