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	$67.57	6.321%	$71.8411	$71.84	$71.85	$71.80
Purchase #2	$242.86	4.832%	$254.595	$254.60	$254.60	$254.60
Purchase #3	$145.27	7.579%	$156.28	$156.28	$156.30	$156.30
Purchase #4	$206.98	7.277%	$222.0419	$222.04	$222.05	$222.00
Purchase #5	$39.92	5.698%	$42.1946	$42.19	$42.20	$42.20
Purchase #6	$11.94	11.384%	$13.2992	$13.30	$13.30	$13.30
Purchase #7	$166.92	11.778%	$186.5798	$186.58	$186.60	$186.60
7 purchase totals =	$881.46		$946.8316	$946.83	$946.90	$946.80