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	$102.73	11.123%	$114.1567	$114.16	$114.15	$114.20
Purchase #2	$182.66	8.546%	$198.2701	$198.27	$198.25	$198.30
Purchase #3	$27.54	6.313%	$29.2786	$29.28	$29.30	$29.30
Purchase #4	$12.33	10.108%	$13.5763	$13.58	$13.60	$13.60
Purchase #5	$114.59	4.868%	$120.1682	$120.17	$120.15	$120.20
Purchase #6	$142.95	7.453%	$153.6041	$153.60	$153.60	$153.60
Purchase #7	$176.40	11.506%	$196.6966	$196.70	$196.70	$196.70
7 purchase totals =	$759.20		$825.7506	$825.76	$825.75	$825.90