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	$54.36	8.741%	$59.1116	$59.11	$59.10	$59.10
Purchase #2	$148.95	12.380%	$167.39	$167.39	$167.40	$167.40
Purchase #3	$117.90	13.451%	$133.7587	$133.76	$133.75	$133.80
Purchase #4	$172.28	8.446%	$186.8308	$186.83	$186.85	$186.80
Purchase #5	$40.68	13.635%	$46.2267	$46.23	$46.25	$46.20
Purchase #6	$58.43	3.414%	$60.4248	$60.42	$60.40	$60.40
Purchase #7	$164.82	4.269%	$171.8562	$171.86	$171.85	$171.90
7 purchase totals =	$757.42		$825.5988	$825.60	$825.60	$825.60