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	$150.80	12.619%	$169.8295	$169.83	$169.85	$169.80
Purchase #2	$91.49	5.164%	$96.2145	$96.21	$96.20	$96.20
Purchase #3	$183.59	3.680%	$190.3461	$190.35	$190.35	$190.30
Purchase #4	$82.69	12.167%	$92.7509	$92.75	$92.75	$92.80
Purchase #5	$103.78	7.786%	$111.8603	$111.86	$111.85	$111.90
Purchase #6	$200.39	4.507%	$209.4216	$209.42	$209.40	$209.40
Purchase #7	$33.71	7.337%	$36.1833	$36.18	$36.20	$36.20
7 purchase totals =	$846.45		$906.6062	$906.60	$906.60	$906.60