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	$195.25	7.158%	$209.226	$209.23	$209.25	$209.20
Purchase #2	$21.58	12.506%	$24.2788	$24.28	$24.30	$24.30
Purchase #3	$147.52	8.305%	$159.7715	$159.77	$159.75	$159.80
Purchase #4	$80.98	6.631%	$86.3498	$86.35	$86.35	$86.30
Purchase #5	$60.83	3.291%	$62.8319	$62.83	$62.85	$62.80
Purchase #6	$123.91	3.157%	$127.8218	$127.82	$127.80	$127.80
Purchase #7	$237.94	13.385%	$269.7883	$269.79	$269.80	$269.80
7 purchase totals =	$868.01		$940.0681	$940.07	$940.10	$940.00