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	$210.98	12.635%	$237.6373	$237.64	$237.65	$237.60
Purchase #2	$162.60	11.720%	$181.6567	$181.66	$181.65	$181.70
Purchase #3	$72.76	13.846%	$82.8343	$82.83	$82.85	$82.80
Purchase #4	$231.34	4.554%	$241.8752	$241.88	$241.90	$241.90
Purchase #5	$51.65	9.255%	$56.4302	$56.43	$56.45	$56.40
Purchase #6	$19.25	11.399%	$21.4443	$21.44	$21.45	$21.40
Purchase #7	$244.97	12.622%	$275.8901	$275.89	$275.90	$275.90
7 purchase totals =	$993.55		$1,097.7681	$1,097.77	$1,097.85	$1,097.70