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	$203.69	3.555%	$210.9312	$210.93	$210.95	$210.90
Purchase #2	$103.88	5.747%	$109.85	$109.85	$109.85	$109.90
Purchase #3	$236.59	3.139%	$244.0166	$244.02	$244.00	$244.00
Purchase #4	$128.84	12.160%	$144.5069	$144.51	$144.50	$144.50
Purchase #5	$18.78	6.431%	$19.9877	$19.99	$20.00	$20.00
Purchase #6	$200.91	5.561%	$212.0826	$212.08	$212.10	$212.10
Purchase #7	$230.60	10.657%	$255.175	$255.18	$255.20	$255.20
7 purchase totals =	$1,123.29		$1,196.5500	$1,196.56	$1,196.60	$1,196.60