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	$104.42	5.247%	$109.8989	$109.90	$109.90	$109.90
Purchase #2	$209.83	12.195%	$235.4188	$235.42	$235.40	$235.40
Purchase #3	$60.56	11.569%	$67.5662	$67.57	$67.55	$67.60
Purchase #4	$187.56	11.855%	$209.7952	$209.80	$209.80	$209.80
Purchase #5	$11.45	3.554%	$11.8569	$11.86	$11.85	$11.90
Purchase #6	$164.94	12.227%	$185.1072	$185.11	$185.10	$185.10
Purchase #7	$64.49	3.329%	$66.6369	$66.64	$66.65	$66.60
7 purchase totals =	$803.25		$886.2801	$886.30	$886.25	$886.30