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	$52.58	3.587%	$54.466	$54.47	$54.45	$54.50
Purchase #2	$219.82	5.776%	$232.5168	$232.52	$232.50	$232.50
Purchase #3	$91.57	9.397%	$100.1748	$100.17	$100.15	$100.20
Purchase #4	$160.92	12.287%	$180.6922	$180.69	$180.70	$180.70
Purchase #5	$161.64	12.401%	$181.685	$181.69	$181.70	$181.70
Purchase #6	$204.28	11.799%	$228.383	$228.38	$228.40	$228.40
Purchase #7	$228.61	4.356%	$238.5683	$238.57	$238.55	$238.60
7 purchase totals =	$1,119.42		$1,216.4861	$1,216.49	$1,216.45	$1,216.60