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	$5.86	5.437%	$6.1786	$6.18	$6.20	$6.20
Purchase #2	$64.86	11.779%	$72.4999	$72.50	$72.50	$72.50
Purchase #3	$105.63	10.216%	$116.4212	$116.42	$116.40	$116.40
Purchase #4	$56.30	10.203%	$62.0443	$62.04	$62.05	$62.00
Purchase #5	$100.94	13.329%	$114.3943	$114.39	$114.40	$114.40
Purchase #6	$176.49	3.506%	$182.6777	$182.68	$182.70	$182.70
Purchase #7	$42.40	11.443%	$47.2518	$47.25	$47.25	$47.30
7 purchase totals =	$552.48		$601.4678	$601.46	$601.50	$601.50