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	$89.40	3.567%	$92.5889	$92.59	$92.60	$92.60
Purchase #2	$213.90	4.644%	$223.8335	$223.83	$223.85	$223.80
Purchase #3	$17.67	4.842%	$18.5256	$18.53	$18.55	$18.50
Purchase #4	$238.91	9.544%	$261.7116	$261.71	$261.70	$261.70
Purchase #5	$91.42	13.730%	$103.972	$103.97	$103.95	$104.00
Purchase #6	$27.80	5.280%	$29.2678	$29.27	$29.25	$29.30
Purchase #7	$243.93	11.604%	$272.2356	$272.24	$272.25	$272.20
7 purchase totals =	$923.03		$1,002.1350	$1,002.14	$1,002.15	$1,002.10