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	$99.40	9.311%	$108.6551	$108.66	$108.65	$108.70
Purchase #2	$232.57	3.765%	$241.3263	$241.33	$241.35	$241.30
Purchase #3	$54.86	7.589%	$59.0233	$59.02	$59.00	$59.00
Purchase #4	$139.57	8.213%	$151.0329	$151.03	$151.05	$151.00
Purchase #5	$119.57	10.253%	$131.8295	$131.83	$131.85	$131.80
Purchase #6	$241.82	13.840%	$275.2879	$275.29	$275.30	$275.30
Purchase #7	$114.62	3.571%	$118.7131	$118.71	$118.70	$118.70
7 purchase totals =	$1,002.41		$1,085.8681	$1,085.87	$1,085.90	$1,085.80