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	$42.86	3.574%	$44.3918	$44.39	$44.40	$44.40
Purchase #2	$33.92	11.527%	$37.83	$37.83	$37.85	$37.80
Purchase #3	$82.89	11.407%	$92.3453	$92.35	$92.35	$92.30
Purchase #4	$64.90	6.801%	$69.3138	$69.31	$69.30	$69.30
Purchase #5	$119.77	8.812%	$130.3241	$130.32	$130.30	$130.30
Purchase #6	$9.60	4.365%	$10.019	$10.02	$10.00	$10.00
Purchase #7	$19.61	6.418%	$20.8686	$20.87	$20.85	$20.90
7 purchase totals =	$373.55		$405.0926	$405.09	$405.05	$405.00