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	$68.50	10.700%	$75.8295	$75.83	$75.85	$75.80
Purchase #2	$96.93	4.644%	$101.4314	$101.43	$101.45	$101.40
Purchase #3	$78.84	4.647%	$82.5037	$82.50	$82.50	$82.50
Purchase #4	$105.82	13.241%	$119.8316	$119.83	$119.85	$119.80
Purchase #5	$44.53	7.586%	$47.908	$47.91	$47.90	$47.90
Purchase #6	$36.51	11.230%	$40.6101	$40.61	$40.60	$40.60
Purchase #7	$146.82	7.178%	$157.3587	$157.36	$157.35	$157.40
7 purchase totals =	$577.95		$625.4730	$625.47	$625.50	$625.40