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	$67.57	9.754%	$74.1608	$74.16	$74.15	$74.20
Purchase #2	$11.78	9.512%	$12.9005	$12.90	$12.90	$12.90
Purchase #3	$219.32	4.747%	$229.7311	$229.73	$229.75	$229.70
Purchase #4	$214.71	12.719%	$242.019	$242.02	$242.00	$242.00
Purchase #5	$62.75	5.138%	$65.9741	$65.97	$65.95	$66.00
Purchase #6	$150.46	4.575%	$157.3435	$157.34	$157.35	$157.30
Purchase #7	$68.88	13.820%	$78.3992	$78.40	$78.40	$78.40
7 purchase totals =	$795.47		$860.5282	$860.52	$860.50	$860.50