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	$128.38	4.274%	$133.867	$133.87	$133.85	$133.90
Purchase #2	$181.47	10.169%	$199.9237	$199.92	$199.90	$199.90
Purchase #3	$99.34	12.636%	$111.8926	$111.89	$111.90	$111.90
Purchase #4	$227.39	9.617%	$249.2581	$249.26	$249.25	$249.30
Purchase #5	$168.61	6.270%	$179.1818	$179.18	$179.20	$179.20
Purchase #6	$193.65	8.318%	$209.7578	$209.76	$209.75	$209.80
Purchase #7	$211.77	12.471%	$238.1798	$238.18	$238.20	$238.20
7 purchase totals =	$1,210.61		$1,322.0608	$1,322.06	$1,322.05	$1,322.20