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	$111.42	5.451%	$117.4935	$117.49	$117.50	$117.50
Purchase #2	$227.39	9.370%	$248.6964	$248.70	$248.70	$248.70
Purchase #3	$238.56	7.626%	$256.7526	$256.75	$256.75	$256.80
Purchase #4	$27.67	13.852%	$31.5028	$31.50	$31.50	$31.50
Purchase #5	$139.84	11.720%	$156.2292	$156.23	$156.25	$156.20
Purchase #6	$156.98	10.701%	$173.7784	$173.78	$173.80	$173.80
Purchase #7	$58.30	4.674%	$61.0249	$61.02	$61.00	$61.00
7 purchase totals =	$960.16		$1,045.4778	$1,045.47	$1,045.50	$1,045.50