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	$87.37	13.669%	$99.3126	$99.31	$99.30	$99.30
Purchase #2	$188.45	13.302%	$213.5176	$213.52	$213.50	$213.50
Purchase #3	$139.73	12.308%	$156.928	$156.93	$156.95	$156.90
Purchase #4	$231.95	10.591%	$256.5158	$256.52	$256.50	$256.50
Purchase #5	$103.97	7.665%	$111.9393	$111.94	$111.95	$111.90
Purchase #6	$202.49	4.593%	$211.7904	$211.79	$211.80	$211.80
Purchase #7	$157.50	5.612%	$166.3389	$166.34	$166.35	$166.30
7 purchase totals =	$1,111.46		$1,216.3426	$1,216.35	$1,216.35	$1,216.20