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	$67.69	10.208%	$74.5998	$74.60	$74.60	$74.60
Purchase #2	$126.49	11.132%	$140.5709	$140.57	$140.55	$140.60
Purchase #3	$73.99	6.523%	$78.8164	$78.82	$78.80	$78.80
Purchase #4	$173.47	4.720%	$181.6578	$181.66	$181.65	$181.70
Purchase #5	$93.38	8.577%	$101.3892	$101.39	$101.40	$101.40
Purchase #6	$61.44	3.183%	$63.3956	$63.40	$63.40	$63.40
Purchase #7	$25.37	8.137%	$27.4344	$27.43	$27.45	$27.40
7 purchase totals =	$621.83		$667.8641	$667.87	$667.85	$667.90