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	$159.79	8.780%	$173.8196	$173.82	$173.80	$173.80
Purchase #2	$89.60	6.609%	$95.5217	$95.52	$95.50	$95.50
Purchase #3	$32.73	5.111%	$34.4028	$34.40	$34.40	$34.40
Purchase #4	$106.41	7.527%	$114.4195	$114.42	$114.40	$114.40
Purchase #5	$219.86	6.470%	$234.0849	$234.08	$234.10	$234.10
Purchase #6	$119.89	6.274%	$127.4119	$127.41	$127.40	$127.40
Purchase #7	$95.94	6.713%	$102.3805	$102.38	$102.40	$102.40
7 purchase totals =	$824.22		$882.0409	$882.03	$882.00	$882.00