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	$182.99	4.120%	$190.5292	$190.53	$190.55	$190.50
Purchase #2	$155.31	11.273%	$172.8181	$172.82	$172.80	$172.80
Purchase #3	$126.92	13.271%	$143.7636	$143.76	$143.75	$143.80
Purchase #4	$116.53	4.231%	$121.4604	$121.46	$121.45	$121.50
Purchase #5	$140.35	4.304%	$146.3907	$146.39	$146.40	$146.40
Purchase #6	$157.98	9.314%	$172.6943	$172.69	$172.70	$172.70
Purchase #7	$59.55	11.829%	$66.5942	$66.59	$66.60	$66.60
7 purchase totals =	$939.63		$1,014.2505	$1,014.24	$1,014.25	$1,014.30