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	$127.60	6.426%	$135.7996	$135.80	$135.80	$135.80
Purchase #2	$100.79	10.622%	$111.4959	$111.50	$111.50	$111.50
Purchase #3	$175.58	8.308%	$190.1672	$190.17	$190.15	$190.20
Purchase #4	$30.63	6.372%	$32.5817	$32.58	$32.60	$32.60
Purchase #5	$158.39	8.339%	$171.5981	$171.60	$171.60	$171.60
Purchase #6	$205.86	4.131%	$214.3641	$214.36	$214.35	$214.40
Purchase #7	$90.82	6.498%	$96.7215	$96.72	$96.70	$96.70
7 purchase totals =	$889.67		$952.7281	$952.73	$952.70	$952.80