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	$105.86	5.142%	$111.3033	$111.30	$111.30	$111.30
Purchase #2	$72.39	12.857%	$81.6972	$81.70	$81.70	$81.70
Purchase #3	$217.53	13.428%	$246.7399	$246.74	$246.75	$246.70
Purchase #4	$133.92	7.795%	$144.3591	$144.36	$144.35	$144.40
Purchase #5	$230.40	3.332%	$238.0769	$238.08	$238.10	$238.10
Purchase #6	$209.60	4.663%	$219.3736	$219.37	$219.35	$219.40
Purchase #7	$103.35	7.419%	$111.0175	$111.02	$111.00	$111.00
7 purchase totals =	$1,073.05		$1,152.5675	$1,152.57	$1,152.55	$1,152.60