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	$131.59	11.381%	$146.5663	$146.57	$146.55	$146.60
Purchase #2	$38.84	6.771%	$41.4699	$41.47	$41.45	$41.50
Purchase #3	$233.49	13.499%	$265.0088	$265.01	$265.00	$265.00
Purchase #4	$158.69	12.648%	$178.7611	$178.76	$178.75	$178.80
Purchase #5	$140.83	6.673%	$150.2276	$150.23	$150.25	$150.20
Purchase #6	$134.72	8.492%	$146.1604	$146.16	$146.15	$146.20
Purchase #7	$35.57	10.390%	$39.2657	$39.27	$39.25	$39.30
7 purchase totals =	$873.73		$967.4598	$967.47	$967.40	$967.60