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	$73.49	12.420%	$82.6175	$82.62	$82.60	$82.60
Purchase #2	$100.56	13.865%	$114.5026	$114.50	$114.50	$114.50
Purchase #3	$15.96	7.835%	$17.2105	$17.21	$17.20	$17.20
Purchase #4	$19.80	4.168%	$20.6253	$20.63	$20.65	$20.60
Purchase #5	$187.86	6.693%	$200.4335	$200.43	$200.45	$200.40
Purchase #6	$217.37	7.458%	$233.5815	$233.58	$233.60	$233.60
Purchase #7	$56.61	7.803%	$61.0273	$61.03	$61.05	$61.00
7 purchase totals =	$671.65		$729.9982	$730.00	$730.05	$729.90