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	$59.55	9.472%	$65.1906	$65.19	$65.20	$65.20
Purchase #2	$204.72	5.667%	$216.3215	$216.32	$216.30	$216.30
Purchase #3	$14.71	3.130%	$15.1704	$15.17	$15.15	$15.20
Purchase #4	$19.48	7.579%	$20.9564	$20.96	$20.95	$21.00
Purchase #5	$30.56	3.142%	$31.5202	$31.52	$31.50	$31.50
Purchase #6	$217.68	4.514%	$227.5061	$227.51	$227.50	$227.50
Purchase #7	$162.89	11.139%	$181.0343	$181.03	$181.05	$181.00
7 purchase totals =	$709.59		$757.6995	$757.70	$757.65	$757.70