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	$75.95	13.128%	$85.9207	$85.92	$85.90	$85.90
Purchase #2	$91.69	4.543%	$95.8555	$95.86	$95.85	$95.90
Purchase #3	$149.93	11.815%	$167.6442	$167.64	$167.65	$167.60
Purchase #4	$205.80	6.729%	$219.6483	$219.65	$219.65	$219.60
Purchase #5	$88.60	11.832%	$99.0832	$99.08	$99.10	$99.10
Purchase #6	$157.45	4.164%	$164.0062	$164.01	$164.00	$164.00
Purchase #7	$149.56	4.196%	$155.8355	$155.84	$155.85	$155.80
7 purchase totals =	$918.98		$987.9936	$988.00	$988.00	$987.90