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	$97.51	11.846%	$109.061	$109.06	$109.05	$109.10
Purchase #2	$21.50	13.224%	$24.3432	$24.34	$24.35	$24.30
Purchase #3	$64.75	10.500%	$71.5488	$71.55	$71.55	$71.50
Purchase #4	$219.88	8.521%	$238.616	$238.62	$238.60	$238.60
Purchase #5	$240.65	8.305%	$260.636	$260.64	$260.65	$260.60
Purchase #6	$96.83	6.677%	$103.2953	$103.30	$103.30	$103.30
Purchase #7	$158.74	5.609%	$167.6437	$167.64	$167.65	$167.60
7 purchase totals =	$899.86		$975.1440	$975.15	$975.15	$975.00