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	$234.61	11.129%	$260.7197	$260.72	$260.70	$260.70
Purchase #2	$149.82	5.820%	$158.5395	$158.54	$158.55	$158.50
Purchase #3	$166.89	3.323%	$172.4358	$172.44	$172.45	$172.40
Purchase #4	$152.83	6.244%	$162.3727	$162.37	$162.35	$162.40
Purchase #5	$136.86	3.667%	$141.8787	$141.88	$141.90	$141.90
Purchase #6	$167.51	4.166%	$174.4885	$174.49	$174.50	$174.50
Purchase #7	$162.71	13.404%	$184.5196	$184.52	$184.50	$184.50
7 purchase totals =	$1,171.23		$1,254.9545	$1,254.96	$1,254.95	$1,254.90