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	$83.62	8.539%	$90.7603	$90.76	$90.75	$90.80
Purchase #2	$240.92	3.456%	$249.2462	$249.25	$249.25	$249.20
Purchase #3	$181.33	7.346%	$194.6505	$194.65	$194.65	$194.70
Purchase #4	$41.72	3.812%	$43.3104	$43.31	$43.30	$43.30
Purchase #5	$176.45	10.435%	$194.8626	$194.86	$194.85	$194.90
Purchase #6	$247.83	4.313%	$258.5189	$258.52	$258.50	$258.50
Purchase #7	$25.65	13.242%	$29.0466	$29.05	$29.05	$29.00
7 purchase totals =	$997.52		$1,060.3955	$1,060.40	$1,060.35	$1,060.40