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	$141.72	13.695%	$161.1286	$161.13	$161.15	$161.10
Purchase #2	$78.33	8.719%	$85.1596	$85.16	$85.15	$85.20
Purchase #3	$50.42	13.161%	$57.0558	$57.06	$57.05	$57.10
Purchase #4	$67.52	6.675%	$72.027	$72.03	$72.05	$72.00
Purchase #5	$191.99	7.108%	$205.6366	$205.64	$205.65	$205.60
Purchase #6	$21.70	13.374%	$24.6022	$24.60	$24.60	$24.60
Purchase #7	$189.82	11.136%	$210.9584	$210.96	$210.95	$211.00
7 purchase totals =	$741.50		$816.5682	$816.58	$816.60	$816.60