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	$157.36	6.130%	$167.0062	$167.01	$167.00	$167.00
Purchase #2	$74.97	10.554%	$82.8823	$82.88	$82.90	$82.90
Purchase #3	$36.57	9.248%	$39.952	$39.95	$39.95	$40.00
Purchase #4	$28.84	12.564%	$32.4635	$32.46	$32.45	$32.50
Purchase #5	$20.55	7.483%	$22.0878	$22.09	$22.10	$22.10
Purchase #6	$52.27	3.710%	$54.2092	$54.21	$54.20	$54.20
Purchase #7	$201.92	10.396%	$222.9116	$222.91	$222.90	$222.90
7 purchase totals =	$572.48		$621.5126	$621.51	$621.50	$621.60