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	$167.84	8.150%	$181.519	$181.52	$181.50	$181.50
Purchase #2	$180.84	3.368%	$186.9307	$186.93	$186.95	$186.90
Purchase #3	$162.70	6.573%	$173.3943	$173.39	$173.40	$173.40
Purchase #4	$173.60	4.525%	$181.4554	$181.46	$181.45	$181.50
Purchase #5	$181.74	10.456%	$200.7427	$200.74	$200.75	$200.70
Purchase #6	$172.98	4.335%	$180.4787	$180.48	$180.50	$180.50
Purchase #7	$43.69	7.663%	$47.038	$47.04	$47.05	$47.00
7 purchase totals =	$1,083.39		$1,151.5588	$1,151.56	$1,151.60	$1,151.50