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	$100.45	5.696%	$106.1716	$106.17	$106.15	$106.20
Purchase #2	$122.86	6.200%	$130.4773	$130.48	$130.50	$130.50
Purchase #3	$215.43	12.150%	$241.6047	$241.60	$241.60	$241.60
Purchase #4	$48.74	8.611%	$52.937	$52.94	$52.95	$52.90
Purchase #5	$143.42	9.125%	$156.5071	$156.51	$156.50	$156.50
Purchase #6	$85.51	7.395%	$91.8335	$91.83	$91.85	$91.80
Purchase #7	$220.35	10.654%	$243.8261	$243.83	$243.85	$243.80
7 purchase totals =	$936.76		$1,023.3573	$1,023.36	$1,023.40	$1,023.30