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	$164.28	13.111%	$185.8188	$185.82	$185.80	$185.80
Purchase #2	$11.94	3.296%	$12.3335	$12.33	$12.35	$12.30
Purchase #3	$150.61	12.608%	$169.5989	$169.60	$169.60	$169.60
Purchase #4	$72.80	12.527%	$81.9197	$81.92	$81.90	$81.90
Purchase #5	$95.79	10.634%	$105.9763	$105.98	$106.00	$106.00
Purchase #6	$224.59	3.293%	$231.9857	$231.99	$232.00	$232.00
Purchase #7	$12.94	7.435%	$13.9021	$13.90	$13.90	$13.90
7 purchase totals =	$732.95		$801.5350	$801.54	$801.55	$801.50