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	$189.61	7.308%	$203.4667	$203.47	$203.45	$203.50
Purchase #2	$96.65	7.191%	$103.6001	$103.60	$103.60	$103.60
Purchase #3	$225.72	8.251%	$244.3442	$244.34	$244.35	$244.30
Purchase #4	$75.48	8.436%	$81.8475	$81.85	$81.85	$81.80
Purchase #5	$38.94	4.723%	$40.7791	$40.78	$40.80	$40.80
Purchase #6	$213.25	9.631%	$233.7881	$233.79	$233.80	$233.80
Purchase #7	$144.66	6.803%	$154.5012	$154.50	$154.50	$154.50
7 purchase totals =	$984.31		$1,062.3269	$1,062.33	$1,062.35	$1,062.30