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	$151.49	13.784%	$172.3714	$172.37	$172.35	$172.40
Purchase #2	$48.48	8.530%	$52.6153	$52.62	$52.60	$52.60
Purchase #3	$182.80	12.292%	$205.2698	$205.27	$205.25	$205.30
Purchase #4	$127.56	6.155%	$135.4113	$135.41	$135.40	$135.40
Purchase #5	$29.79	4.761%	$31.2083	$31.21	$31.20	$31.20
Purchase #6	$186.93	5.231%	$196.7083	$196.71	$196.70	$196.70
Purchase #7	$136.30	9.297%	$148.9718	$148.97	$148.95	$149.00
7 purchase totals =	$863.35		$942.5562	$942.56	$942.45	$942.60