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	$104.67	9.771%	$114.8973	$114.90	$114.90	$114.90
Purchase #2	$10.91	3.123%	$11.2507	$11.25	$11.25	$11.30
Purchase #3	$158.91	3.783%	$164.9216	$164.92	$164.90	$164.90
Purchase #4	$130.60	12.474%	$146.891	$146.89	$146.90	$146.90
Purchase #5	$49.41	13.706%	$56.1821	$56.18	$56.20	$56.20
Purchase #6	$156.41	9.842%	$171.8039	$171.80	$171.80	$171.80
Purchase #7	$46.59	11.285%	$51.8477	$51.85	$51.85	$51.80
7 purchase totals =	$657.50		$717.7943	$717.79	$717.80	$717.80