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	$123.46	3.611%	$127.9181	$127.92	$127.90	$127.90
Purchase #2	$105.81	5.566%	$111.6994	$111.70	$111.70	$111.70
Purchase #3	$218.66	6.126%	$232.0551	$232.06	$232.05	$232.10
Purchase #4	$104.85	8.345%	$113.5997	$113.60	$113.60	$113.60
Purchase #5	$85.45	5.663%	$90.289	$90.29	$90.30	$90.30
Purchase #6	$57.79	11.759%	$64.5855	$64.59	$64.60	$64.60
Purchase #7	$130.42	12.317%	$146.4838	$146.48	$146.50	$146.50
7 purchase totals =	$826.44		$886.6306	$886.64	$886.65	$886.70