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	$148.56	10.669%	$164.4099	$164.41	$164.40	$164.40
Purchase #2	$237.97	5.115%	$250.1422	$250.14	$250.15	$250.10
Purchase #3	$171.27	11.618%	$191.1681	$191.17	$191.15	$191.20
Purchase #4	$155.49	13.696%	$176.7859	$176.79	$176.80	$176.80
Purchase #5	$56.29	7.643%	$60.5922	$60.59	$60.60	$60.60
Purchase #6	$120.32	9.739%	$132.038	$132.04	$132.05	$132.00
Purchase #7	$175.64	11.699%	$196.1881	$196.19	$196.20	$196.20
7 purchase totals =	$1,065.54		$1,171.3244	$1,171.33	$1,171.35	$1,171.30