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	$14.47	3.262%	$14.942	$14.94	$14.95	$14.90
Purchase #2	$33.39	11.207%	$37.132	$37.13	$37.15	$37.10
Purchase #3	$98.52	8.478%	$106.8725	$106.87	$106.85	$106.90
Purchase #4	$160.49	11.435%	$178.842	$178.84	$178.85	$178.80
Purchase #5	$135.38	6.547%	$144.2433	$144.24	$144.25	$144.20
Purchase #6	$44.76	4.256%	$46.665	$46.67	$46.65	$46.70
Purchase #7	$145.42	7.636%	$156.5243	$156.52	$156.50	$156.50
7 purchase totals =	$632.43		$685.2211	$685.21	$685.20	$685.10