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	$125.65	8.613%	$136.4722	$136.47	$136.45	$136.50
Purchase #2	$161.75	10.534%	$178.7887	$178.79	$178.80	$178.80
Purchase #3	$94.83	11.342%	$105.5856	$105.59	$105.60	$105.60
Purchase #4	$149.49	13.666%	$169.9193	$169.92	$169.90	$169.90
Purchase #5	$122.25	9.293%	$133.6107	$133.61	$133.60	$133.60
Purchase #6	$156.93	8.700%	$170.5829	$170.58	$170.60	$170.60
Purchase #7	$102.93	6.754%	$109.8819	$109.88	$109.90	$109.90
7 purchase totals =	$913.83		$1,004.8413	$1,004.84	$1,004.85	$1,004.90