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	$32.60	10.445%	$36.0051	$36.01	$36.00	$36.00
Purchase #2	$109.68	12.451%	$123.3363	$123.34	$123.35	$123.30
Purchase #3	$185.66	11.312%	$206.6619	$206.66	$206.65	$206.70
Purchase #4	$190.55	4.742%	$199.5859	$199.59	$199.60	$199.60
Purchase #5	$52.39	13.485%	$59.4548	$59.45	$59.45	$59.50
Purchase #6	$72.54	3.873%	$75.3495	$75.35	$75.35	$75.30
Purchase #7	$95.92	5.114%	$100.8253	$100.83	$100.85	$100.80
7 purchase totals =	$739.34		$801.2188	$801.23	$801.25	$801.20