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	$71.95	8.845%	$78.314	$78.31	$78.30	$78.30
Purchase #2	$145.58	12.762%	$164.1589	$164.16	$164.15	$164.20
Purchase #3	$63.55	10.735%	$70.3721	$70.37	$70.35	$70.40
Purchase #4	$136.86	7.353%	$146.9233	$146.92	$146.90	$146.90
Purchase #5	$34.61	6.519%	$36.8662	$36.87	$36.85	$36.90
Purchase #6	$38.45	11.263%	$42.7806	$42.78	$42.80	$42.80
Purchase #7	$190.37	7.306%	$204.2784	$204.28	$204.30	$204.30
7 purchase totals =	$681.37		$743.6935	$743.69	$743.65	$743.80