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	$41.95	13.609%	$47.659	$47.66	$47.65	$47.70
Purchase #2	$52.26	4.446%	$54.5835	$54.58	$54.60	$54.60
Purchase #3	$41.29	3.781%	$42.8512	$42.85	$42.85	$42.90
Purchase #4	$179.75	8.200%	$194.4895	$194.49	$194.50	$194.50
Purchase #5	$97.28	6.265%	$103.3746	$103.37	$103.35	$103.40
Purchase #6	$98.71	12.745%	$111.2906	$111.29	$111.30	$111.30
Purchase #7	$161.25	8.173%	$174.429	$174.43	$174.45	$174.40
7 purchase totals =	$672.49		$728.6774	$728.67	$728.70	$728.80