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	$162.80	6.308%	$173.0694	$173.07	$173.05	$173.10
Purchase #2	$57.49	11.792%	$64.2692	$64.27	$64.25	$64.30
Purchase #3	$195.60	13.677%	$222.3522	$222.35	$222.35	$222.40
Purchase #4	$82.47	7.739%	$88.8524	$88.85	$88.85	$88.90
Purchase #5	$70.43	10.833%	$78.0597	$78.06	$78.05	$78.10
Purchase #6	$167.38	13.184%	$189.4474	$189.45	$189.45	$189.40
Purchase #7	$111.44	13.612%	$126.6092	$126.61	$126.60	$126.60
7 purchase totals =	$847.61		$942.6595	$942.66	$942.60	$942.80