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	$192.50	4.363%	$200.8988	$200.90	$200.90	$200.90
Purchase #2	$181.60	6.748%	$193.8544	$193.85	$193.85	$193.90
Purchase #3	$200.32	10.565%	$221.4838	$221.48	$221.50	$221.50
Purchase #4	$92.74	5.789%	$98.1087	$98.11	$98.10	$98.10
Purchase #5	$37.95	9.163%	$41.4274	$41.43	$41.45	$41.40
Purchase #6	$128.36	12.263%	$144.1008	$144.10	$144.10	$144.10
Purchase #7	$241.91	5.592%	$255.4376	$255.44	$255.45	$255.40
7 purchase totals =	$1,075.38		$1,155.3115	$1,155.31	$1,155.35	$1,155.30