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	$190.87	13.607%	$216.8417	$216.84	$216.85	$216.80
Purchase #2	$95.39	12.656%	$107.4626	$107.46	$107.45	$107.50
Purchase #3	$184.71	11.257%	$205.5028	$205.50	$205.50	$205.50
Purchase #4	$98.82	5.418%	$104.1741	$104.17	$104.15	$104.20
Purchase #5	$10.70	12.494%	$12.0369	$12.04	$12.05	$12.00
Purchase #6	$222.45	4.871%	$233.2855	$233.29	$233.30	$233.30
Purchase #7	$186.40	5.502%	$196.6557	$196.66	$196.65	$196.70
7 purchase totals =	$989.34		$1,075.9593	$1,075.96	$1,075.95	$1,076.00