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	$172.94	6.116%	$183.517	$183.52	$183.50	$183.50
Purchase #2	$33.44	12.220%	$37.5264	$37.53	$37.55	$37.50
Purchase #3	$171.50	13.131%	$194.0197	$194.02	$194.00	$194.00
Purchase #4	$152.83	4.446%	$159.6248	$159.62	$159.60	$159.60
Purchase #5	$127.55	5.465%	$134.5206	$134.52	$134.50	$134.50
Purchase #6	$165.73	5.864%	$175.4484	$175.45	$175.45	$175.40
Purchase #7	$132.25	3.638%	$137.0613	$137.06	$137.05	$137.10
7 purchase totals =	$956.24		$1,021.7182	$1,021.72	$1,021.65	$1,021.60