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	$215.69	12.151%	$241.8985	$241.90	$241.90	$241.90
Purchase #2	$62.73	5.253%	$66.0252	$66.03	$66.05	$66.00
Purchase #3	$27.30	3.722%	$28.3161	$28.32	$28.30	$28.30
Purchase #4	$165.73	13.329%	$187.8202	$187.82	$187.80	$187.80
Purchase #5	$36.44	11.152%	$40.5038	$40.50	$40.50	$40.50
Purchase #6	$183.82	6.480%	$195.7315	$195.73	$195.75	$195.70
Purchase #7	$191.58	4.437%	$200.0804	$200.08	$200.10	$200.10
7 purchase totals =	$883.29		$960.3757	$960.38	$960.40	$960.30