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	$174.42	8.108%	$188.562	$188.56	$188.55	$188.60
Purchase #2	$56.81	11.578%	$63.3875	$63.39	$63.40	$63.40
Purchase #3	$99.94	6.292%	$106.2282	$106.23	$106.25	$106.20
Purchase #4	$144.42	5.195%	$151.9226	$151.92	$151.90	$151.90
Purchase #5	$116.66	12.318%	$131.0302	$131.03	$131.05	$131.00
Purchase #6	$62.55	13.115%	$70.7534	$70.75	$70.75	$70.80
Purchase #7	$37.78	7.367%	$40.5633	$40.56	$40.55	$40.60
7 purchase totals =	$692.58		$752.4472	$752.44	$752.45	$752.50