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	$97.63	3.535%	$101.0812	$101.08	$101.10	$101.10
Purchase #2	$189.79	10.278%	$209.2966	$209.30	$209.30	$209.30
Purchase #3	$124.28	5.862%	$131.5653	$131.57	$131.55	$131.60
Purchase #4	$77.56	4.733%	$81.2309	$81.23	$81.25	$81.20
Purchase #5	$101.39	9.850%	$111.3769	$111.38	$111.40	$111.40
Purchase #6	$156.93	9.826%	$172.3499	$172.35	$172.35	$172.30
Purchase #7	$99.86	4.361%	$104.2149	$104.21	$104.20	$104.20
7 purchase totals =	$847.44		$911.1157	$911.12	$911.15	$911.10