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	$144.48	6.151%	$153.367	$153.37	$153.35	$153.40
Purchase #2	$30.52	7.410%	$32.7815	$32.78	$32.80	$32.80
Purchase #3	$183.30	7.449%	$196.954	$196.95	$196.95	$197.00
Purchase #4	$27.65	12.795%	$31.1878	$31.19	$31.20	$31.20
Purchase #5	$126.46	10.830%	$140.1556	$140.16	$140.15	$140.20
Purchase #6	$66.56	10.544%	$73.5781	$73.58	$73.60	$73.60
Purchase #7	$129.45	12.669%	$145.85	$145.85	$145.85	$145.90
7 purchase totals =	$708.42		$773.8740	$773.88	$773.90	$774.10