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	$157.29	7.362%	$168.8697	$168.87	$168.85	$168.90
Purchase #2	$197.57	13.687%	$224.6114	$224.61	$224.60	$224.60
Purchase #3	$139.42	10.706%	$154.3463	$154.35	$154.35	$154.30
Purchase #4	$151.52	8.411%	$164.2643	$164.26	$164.25	$164.30
Purchase #5	$141.63	7.523%	$152.2848	$152.28	$152.30	$152.30
Purchase #6	$78.56	5.160%	$82.6137	$82.61	$82.60	$82.60
Purchase #7	$248.87	5.211%	$261.8386	$261.84	$261.85	$261.80
7 purchase totals =	$1,114.86		$1,208.8288	$1,208.82	$1,208.80	$1,208.80