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	$19.52	3.103%	$20.1257	$20.13	$20.15	$20.10
Purchase #2	$156.38	4.335%	$163.1591	$163.16	$163.15	$163.20
Purchase #3	$212.92	6.831%	$227.4646	$227.46	$227.45	$227.50
Purchase #4	$155.46	11.470%	$173.2913	$173.29	$173.30	$173.30
Purchase #5	$31.66	6.158%	$33.6096	$33.61	$33.60	$33.60
Purchase #6	$164.34	11.367%	$183.0205	$183.02	$183.00	$183.00
Purchase #7	$188.62	12.322%	$211.8618	$211.86	$211.85	$211.90
7 purchase totals =	$928.90		$1,012.5326	$1,012.53	$1,012.50	$1,012.60