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	$169.50	10.225%	$186.8314	$186.83	$186.85	$186.80
Purchase #2	$76.66	9.720%	$84.1114	$84.11	$84.10	$84.10
Purchase #3	$44.51	4.528%	$46.5254	$46.53	$46.55	$46.50
Purchase #4	$33.69	9.522%	$36.898	$36.90	$36.90	$36.90
Purchase #5	$121.38	5.104%	$127.5752	$127.58	$127.60	$127.60
Purchase #6	$153.47	13.635%	$174.3956	$174.40	$174.40	$174.40
Purchase #7	$122.65	4.211%	$127.8148	$127.81	$127.80	$127.80
7 purchase totals =	$721.86		$784.1518	$784.16	$784.20	$784.10