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	$208.61	9.696%	$228.8368	$228.84	$228.85	$228.80
Purchase #2	$13.62	7.352%	$14.6213	$14.62	$14.60	$14.60
Purchase #3	$201.56	13.736%	$229.2463	$229.25	$229.25	$229.20
Purchase #4	$107.60	3.403%	$111.2616	$111.26	$111.25	$111.30
Purchase #5	$191.86	4.421%	$200.3421	$200.34	$200.35	$200.30
Purchase #6	$17.77	6.225%	$18.8762	$18.88	$18.90	$18.90
Purchase #7	$117.75	11.669%	$131.4902	$131.49	$131.50	$131.50
7 purchase totals =	$858.77		$934.6745	$934.68	$934.70	$934.60