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	$239.53	7.678%	$257.9211	$257.92	$257.90	$257.90
Purchase #2	$30.84	5.330%	$32.4838	$32.48	$32.50	$32.50
Purchase #3	$137.75	7.363%	$147.8925	$147.89	$147.90	$147.90
Purchase #4	$131.90	13.107%	$149.1881	$149.19	$149.20	$149.20
Purchase #5	$70.69	3.183%	$72.9401	$72.94	$72.95	$72.90
Purchase #6	$166.90	3.112%	$172.0939	$172.09	$172.10	$172.10
Purchase #7	$178.84	9.795%	$196.3574	$196.36	$196.35	$196.40
7 purchase totals =	$956.45		$1,028.8769	$1,028.87	$1,028.90	$1,028.90