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	$242.28	6.803%	$258.7623	$258.76	$258.75	$258.80
Purchase #2	$94.46	6.467%	$100.5687	$100.57	$100.55	$100.60
Purchase #3	$147.74	8.692%	$160.5816	$160.58	$160.60	$160.60
Purchase #4	$113.75	12.741%	$128.2429	$128.24	$128.25	$128.20
Purchase #5	$154.92	10.491%	$171.1727	$171.17	$171.15	$171.20
Purchase #6	$208.48	6.706%	$222.4607	$222.46	$222.45	$222.50
Purchase #7	$31.44	6.341%	$33.4336	$33.43	$33.45	$33.40
7 purchase totals =	$993.07		$1,075.2225	$1,075.21	$1,075.20	$1,075.30