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	$89.63	5.192%	$94.2836	$94.28	$94.30	$94.30
Purchase #2	$158.97	11.104%	$176.622	$176.62	$176.60	$176.60
Purchase #3	$17.29	7.384%	$18.5667	$18.57	$18.55	$18.60
Purchase #4	$167.53	5.132%	$176.1276	$176.13	$176.15	$176.10
Purchase #5	$204.98	8.739%	$222.8932	$222.89	$222.90	$222.90
Purchase #6	$6.60	11.497%	$7.3588	$7.36	$7.35	$7.40
Purchase #7	$64.37	4.821%	$67.4733	$67.47	$67.45	$67.50
7 purchase totals =	$709.37		$763.3252	$763.32	$763.30	$763.40