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	$146.50	3.804%	$152.0729	$152.07	$152.05	$152.10
Purchase #2	$132.59	13.131%	$150.0004	$150.00	$150.00	$150.00
Purchase #3	$242.88	12.172%	$272.4434	$272.44	$272.45	$272.40
Purchase #4	$143.68	6.331%	$152.7764	$152.78	$152.80	$152.80
Purchase #5	$104.48	6.604%	$111.3799	$111.38	$111.40	$111.40
Purchase #6	$81.74	9.518%	$89.52	$89.52	$89.50	$89.50
Purchase #7	$41.92	5.861%	$44.3769	$44.38	$44.40	$44.40
7 purchase totals =	$893.79		$972.5699	$972.57	$972.60	$972.60