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	$199.86	8.833%	$217.5136	$217.51	$217.50	$217.50
Purchase #2	$64.27	4.787%	$67.3466	$67.35	$67.35	$67.30
Purchase #3	$168.28	3.107%	$173.5085	$173.51	$173.50	$173.50
Purchase #4	$34.98	11.141%	$38.8771	$38.88	$38.90	$38.90
Purchase #5	$10.50	3.243%	$10.8405	$10.84	$10.85	$10.80
Purchase #6	$247.91	8.174%	$268.1742	$268.17	$268.15	$268.20
Purchase #7	$27.63	13.463%	$31.3498	$31.35	$31.35	$31.30
7 purchase totals =	$753.43		$807.6103	$807.61	$807.60	$807.50