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	$207.54	7.464%	$223.0308	$223.03	$223.05	$223.00
Purchase #2	$33.31	12.790%	$37.5703	$37.57	$37.55	$37.60
Purchase #3	$157.56	9.847%	$173.0749	$173.07	$173.05	$173.10
Purchase #4	$148.66	8.252%	$160.9274	$160.93	$160.95	$160.90
Purchase #5	$127.67	3.247%	$131.8154	$131.82	$131.80	$131.80
Purchase #6	$219.84	6.417%	$233.9471	$233.95	$233.95	$233.90
Purchase #7	$186.73	13.712%	$212.3344	$212.33	$212.35	$212.30
7 purchase totals =	$1,081.31		$1,172.7003	$1,172.70	$1,172.70	$1,172.60