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	$32.81	9.180%	$35.822	$35.82	$35.80	$35.80
Purchase #2	$86.89	10.672%	$96.1629	$96.16	$96.15	$96.20
Purchase #3	$197.65	10.188%	$217.7866	$217.79	$217.80	$217.80
Purchase #4	$182.90	7.292%	$196.2371	$196.24	$196.25	$196.20
Purchase #5	$172.48	13.798%	$196.2788	$196.28	$196.30	$196.30
Purchase #6	$37.76	10.156%	$41.5949	$41.59	$41.60	$41.60
Purchase #7	$160.65	10.504%	$177.5247	$177.52	$177.50	$177.50
7 purchase totals =	$871.14		$961.4070	$961.40	$961.40	$961.40