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	$200.28	9.545%	$219.3967	$219.40	$219.40	$219.40
Purchase #2	$159.71	12.362%	$179.4534	$179.45	$179.45	$179.50
Purchase #3	$27.50	3.791%	$28.5425	$28.54	$28.55	$28.50
Purchase #4	$70.78	11.840%	$79.1604	$79.16	$79.15	$79.20
Purchase #5	$14.91	11.257%	$16.5884	$16.59	$16.60	$16.60
Purchase #6	$151.70	5.750%	$160.4228	$160.42	$160.40	$160.40
Purchase #7	$100.89	10.385%	$111.3674	$111.37	$111.35	$111.40
7 purchase totals =	$725.77		$794.9316	$794.93	$794.90	$795.00