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	$102.88	13.513%	$116.7822	$116.78	$116.80	$116.80
Purchase #2	$213.66	5.670%	$225.7745	$225.77	$225.75	$225.80
Purchase #3	$157.96	4.203%	$164.5991	$164.60	$164.60	$164.60
Purchase #4	$55.95	3.474%	$57.8937	$57.89	$57.90	$57.90
Purchase #5	$94.25	5.463%	$99.3989	$99.40	$99.40	$99.40
Purchase #6	$161.52	3.571%	$167.2879	$167.29	$167.30	$167.30
Purchase #7	$202.54	8.665%	$220.0901	$220.09	$220.10	$220.10
7 purchase totals =	$988.76		$1,051.8264	$1,051.82	$1,051.85	$1,051.90