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	$182.65	13.222%	$206.8	$206.80	$206.80	$206.80
Purchase #2	$183.50	10.802%	$203.3217	$203.32	$203.30	$203.30
Purchase #3	$85.70	11.660%	$95.6926	$95.69	$95.70	$95.70
Purchase #4	$42.48	7.387%	$45.618	$45.62	$45.60	$45.60
Purchase #5	$216.82	3.342%	$224.0661	$224.07	$224.05	$224.10
Purchase #6	$74.77	4.419%	$78.0741	$78.07	$78.05	$78.10
Purchase #7	$219.86	5.653%	$232.2887	$232.29	$232.30	$232.30
7 purchase totals =	$1,005.78		$1,085.8612	$1,085.86	$1,085.80	$1,085.90