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	$233.96	13.111%	$264.6345	$264.63	$264.65	$264.60
Purchase #2	$74.62	3.688%	$77.372	$77.37	$77.35	$77.40
Purchase #3	$175.48	8.582%	$190.5397	$190.54	$190.55	$190.50
Purchase #4	$138.79	9.464%	$151.9251	$151.93	$151.95	$151.90
Purchase #5	$37.85	5.215%	$39.8239	$39.82	$39.80	$39.80
Purchase #6	$90.83	6.436%	$96.6758	$96.68	$96.70	$96.70
Purchase #7	$196.43	4.680%	$205.6229	$205.62	$205.60	$205.60
7 purchase totals =	$947.96		$1,026.5939	$1,026.59	$1,026.60	$1,026.50