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	$34.66	10.550%	$38.3166	$38.32	$38.30	$38.30
Purchase #2	$62.66	12.745%	$70.646	$70.65	$70.65	$70.60
Purchase #3	$77.60	6.766%	$82.8504	$82.85	$82.85	$82.90
Purchase #4	$67.78	4.215%	$70.6369	$70.64	$70.65	$70.60
Purchase #5	$46.91	8.341%	$50.8228	$50.82	$50.80	$50.80
Purchase #6	$27.47	13.287%	$31.1199	$31.12	$31.10	$31.10
Purchase #7	$87.89	3.528%	$90.9908	$90.99	$91.00	$91.00
7 purchase totals =	$404.97		$435.3834	$435.39	$435.35	$435.30