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	$152.65	5.678%	$161.3175	$161.32	$161.30	$161.30
Purchase #2	$19.69	6.246%	$20.9198	$20.92	$20.90	$20.90
Purchase #3	$37.33	3.821%	$38.7564	$38.76	$38.75	$38.80
Purchase #4	$143.84	9.785%	$157.9147	$157.91	$157.90	$157.90
Purchase #5	$17.55	5.780%	$18.5644	$18.56	$18.55	$18.60
Purchase #6	$39.38	3.475%	$40.7485	$40.75	$40.75	$40.70
Purchase #7	$103.80	7.360%	$111.4397	$111.44	$111.45	$111.40
7 purchase totals =	$514.24		$549.6610	$549.66	$549.60	$549.60