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	$246.68	7.753%	$265.8051	$265.81	$265.80	$265.80
Purchase #2	$57.45	7.770%	$61.9139	$61.91	$61.90	$61.90
Purchase #3	$62.55	4.376%	$65.2872	$65.29	$65.30	$65.30
Purchase #4	$104.39	9.556%	$114.3655	$114.37	$114.35	$114.40
Purchase #5	$149.78	4.342%	$156.2834	$156.28	$156.30	$156.30
Purchase #6	$18.48	5.247%	$19.4496	$19.45	$19.45	$19.40
Purchase #7	$101.72	3.731%	$105.5152	$105.52	$105.50	$105.50
7 purchase totals =	$741.05		$788.6199	$788.63	$788.60	$788.60