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	$164.46	12.719%	$185.3777	$185.38	$185.40	$185.40
Purchase #2	$170.39	9.506%	$186.5873	$186.59	$186.60	$186.60
Purchase #3	$99.33	6.788%	$106.0725	$106.07	$106.05	$106.10
Purchase #4	$193.79	7.613%	$208.5432	$208.54	$208.55	$208.50
Purchase #5	$100.42	7.734%	$108.1865	$108.19	$108.20	$108.20
Purchase #6	$238.83	6.293%	$253.8596	$253.86	$253.85	$253.90
Purchase #7	$133.58	10.635%	$147.7862	$147.79	$147.80	$147.80
7 purchase totals =	$1,100.80		$1,196.4130	$1,196.42	$1,196.45	$1,196.50