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	$10.49	9.345%	$11.4703	$11.47	$11.45	$11.50
Purchase #2	$210.94	5.722%	$223.01	$223.01	$223.00	$223.00
Purchase #3	$121.28	5.245%	$127.6411	$127.64	$127.65	$127.60
Purchase #4	$73.36	4.289%	$76.5064	$76.51	$76.50	$76.50
Purchase #5	$86.89	9.863%	$95.46	$95.46	$95.45	$95.50
Purchase #6	$191.53	4.627%	$200.3921	$200.39	$200.40	$200.40
Purchase #7	$219.66	12.668%	$247.4865	$247.49	$247.50	$247.50
7 purchase totals =	$914.15		$981.9664	$981.97	$981.95	$982.00