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	$230.93	5.839%	$244.414	$244.41	$244.40	$244.40
Purchase #2	$209.67	12.202%	$235.2539	$235.25	$235.25	$235.30
Purchase #3	$140.50	7.286%	$150.7368	$150.74	$150.75	$150.70
Purchase #4	$34.95	11.161%	$38.8508	$38.85	$38.85	$38.90
Purchase #5	$157.30	4.577%	$164.4996	$164.50	$164.50	$164.50
Purchase #6	$153.57	7.599%	$165.2398	$165.24	$165.25	$165.20
Purchase #7	$141.50	10.578%	$156.4679	$156.47	$156.45	$156.50
7 purchase totals =	$1,068.42		$1,155.4628	$1,155.46	$1,155.45	$1,155.50