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	$190.73	3.262%	$196.9516	$196.95	$196.95	$197.00
Purchase #2	$81.32	4.537%	$85.0095	$85.01	$85.00	$85.00
Purchase #3	$20.74	11.774%	$23.1819	$23.18	$23.20	$23.20
Purchase #4	$243.61	6.324%	$259.0159	$259.02	$259.00	$259.00
Purchase #5	$20.31	7.253%	$21.7831	$21.78	$21.80	$21.80
Purchase #6	$96.40	13.169%	$109.0949	$109.09	$109.10	$109.10
Purchase #7	$89.43	6.762%	$95.4773	$95.48	$95.50	$95.50
7 purchase totals =	$742.54		$790.5142	$790.51	$790.55	$790.60