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	$192.60	8.709%	$209.3735	$209.37	$209.35	$209.40
Purchase #2	$123.32	3.682%	$127.8606	$127.86	$127.85	$127.90
Purchase #3	$52.51	7.638%	$56.5207	$56.52	$56.50	$56.50
Purchase #4	$116.96	4.512%	$122.2372	$122.24	$122.25	$122.20
Purchase #5	$157.27	13.536%	$178.5581	$178.56	$178.55	$178.60
Purchase #6	$192.95	13.690%	$219.3649	$219.36	$219.35	$219.40
Purchase #7	$198.38	7.565%	$213.3874	$213.39	$213.40	$213.40
7 purchase totals =	$1,033.99		$1,127.3024	$1,127.30	$1,127.25	$1,127.40