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	$81.58	13.532%	$92.6194	$92.62	$92.60	$92.60
Purchase #2	$42.59	11.254%	$47.3831	$47.38	$47.40	$47.40
Purchase #3	$73.71	6.459%	$78.4709	$78.47	$78.45	$78.50
Purchase #4	$93.80	12.812%	$105.8177	$105.82	$105.80	$105.80
Purchase #5	$12.48	8.205%	$13.504	$13.50	$13.50	$13.50
Purchase #6	$180.32	4.718%	$188.8275	$188.83	$188.85	$188.80
Purchase #7	$219.38	7.217%	$235.2127	$235.21	$235.20	$235.20
7 purchase totals =	$703.86		$761.8353	$761.83	$761.80	$761.80