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	$243.77	8.574%	$264.6708	$264.67	$264.65	$264.70
Purchase #2	$93.71	4.163%	$97.6111	$97.61	$97.60	$97.60
Purchase #3	$186.81	10.199%	$205.8628	$205.86	$205.85	$205.90
Purchase #4	$43.57	4.693%	$45.6147	$45.61	$45.60	$45.60
Purchase #5	$13.49	5.602%	$14.2457	$14.25	$14.25	$14.20
Purchase #6	$53.51	6.292%	$56.8768	$56.88	$56.90	$56.90
Purchase #7	$111.86	10.759%	$123.895	$123.90	$123.90	$123.90
7 purchase totals =	$746.72		$808.7769	$808.78	$808.75	$808.80