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	$100.44	4.801%	$105.2621	$105.26	$105.25	$105.30
Purchase #2	$44.32	9.465%	$48.5149	$48.51	$48.50	$48.50
Purchase #3	$242.25	11.380%	$269.8181	$269.82	$269.80	$269.80
Purchase #4	$102.91	13.279%	$116.5754	$116.58	$116.60	$116.60
Purchase #5	$231.91	7.497%	$249.2963	$249.30	$249.30	$249.30
Purchase #6	$137.89	12.705%	$155.4089	$155.41	$155.40	$155.40
Purchase #7	$126.60	10.834%	$140.3158	$140.32	$140.30	$140.30
7 purchase totals =	$986.32		$1,085.1915	$1,085.20	$1,085.15	$1,085.20