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	$76.47	11.209%	$85.0415	$85.04	$85.05	$85.00
Purchase #2	$129.54	11.322%	$144.2065	$144.21	$144.20	$144.20
Purchase #3	$231.84	9.783%	$254.5209	$254.52	$254.50	$254.50
Purchase #4	$63.78	6.466%	$67.904	$67.90	$67.90	$67.90
Purchase #5	$99.39	9.382%	$108.7148	$108.71	$108.70	$108.70
Purchase #6	$22.77	13.764%	$25.9041	$25.90	$25.90	$25.90
Purchase #7	$71.91	13.132%	$81.3532	$81.35	$81.35	$81.40
7 purchase totals =	$695.70		$767.6450	$767.63	$767.60	$767.60