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	$214.86	3.848%	$223.1278	$223.13	$223.15	$223.10
Purchase #2	$74.68	3.272%	$77.1235	$77.12	$77.10	$77.10
Purchase #3	$193.59	6.173%	$205.5403	$205.54	$205.55	$205.50
Purchase #4	$131.44	8.596%	$142.7386	$142.74	$142.75	$142.70
Purchase #5	$203.90	11.864%	$228.0907	$228.09	$228.10	$228.10
Purchase #6	$154.56	12.242%	$173.4812	$173.48	$173.50	$173.50
Purchase #7	$40.47	5.679%	$42.7683	$42.77	$42.75	$42.80
7 purchase totals =	$1,013.50		$1,092.8704	$1,092.87	$1,092.90	$1,092.80