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	$132.53	7.790%	$142.8541	$142.85	$142.85	$142.90
Purchase #2	$76.74	5.570%	$81.0144	$81.01	$81.00	$81.00
Purchase #3	$37.85	11.123%	$42.0601	$42.06	$42.05	$42.10
Purchase #4	$25.69	7.599%	$27.6422	$27.64	$27.65	$27.60
Purchase #5	$200.80	6.816%	$214.4865	$214.49	$214.50	$214.50
Purchase #6	$151.92	10.503%	$167.8762	$167.88	$167.90	$167.90
Purchase #7	$58.82	5.136%	$61.841	$61.84	$61.85	$61.80
7 purchase totals =	$684.35		$737.7745	$737.77	$737.80	$737.80