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	$72.33	13.758%	$82.2812	$82.28	$82.30	$82.30
Purchase #2	$208.61	6.553%	$222.2802	$222.28	$222.30	$222.30
Purchase #3	$220.86	10.774%	$244.6555	$244.66	$244.65	$244.70
Purchase #4	$123.97	8.725%	$134.7864	$134.79	$134.80	$134.80
Purchase #5	$54.88	5.646%	$57.9785	$57.98	$58.00	$58.00
Purchase #6	$93.54	10.561%	$103.4188	$103.42	$103.40	$103.40
Purchase #7	$154.64	3.687%	$160.3416	$160.34	$160.35	$160.30
7 purchase totals =	$928.83		$1,005.7422	$1,005.75	$1,005.80	$1,005.80