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	$95.85	9.461%	$104.9184	$104.92	$104.90	$104.90
Purchase #2	$152.46	10.700%	$168.7732	$168.77	$168.75	$168.80
Purchase #3	$52.39	3.443%	$54.1938	$54.19	$54.20	$54.20
Purchase #4	$122.69	11.650%	$136.9834	$136.98	$137.00	$137.00
Purchase #5	$68.66	4.421%	$71.6955	$71.70	$71.70	$71.70
Purchase #6	$166.93	9.208%	$182.3009	$182.30	$182.30	$182.30
Purchase #7	$95.45	5.601%	$100.7962	$100.80	$100.80	$100.80
7 purchase totals =	$754.43		$819.6614	$819.66	$819.65	$819.70