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	$150.43	4.676%	$157.4641	$157.46	$157.45	$157.50
Purchase #2	$76.55	13.130%	$86.601	$86.60	$86.60	$86.60
Purchase #3	$30.75	8.439%	$33.345	$33.35	$33.35	$33.30
Purchase #4	$88.99	12.665%	$100.2606	$100.26	$100.25	$100.30
Purchase #5	$128.38	10.544%	$141.9164	$141.92	$141.90	$141.90
Purchase #6	$188.66	11.676%	$210.6879	$210.69	$210.70	$210.70
Purchase #7	$10.40	6.807%	$11.1079	$11.11	$11.10	$11.10
7 purchase totals =	$674.16		$741.3829	$741.39	$741.35	$741.40