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	$55.63	12.671%	$62.6789	$62.68	$62.70	$62.70
Purchase #2	$70.40	8.420%	$76.3277	$76.33	$76.35	$76.30
Purchase #3	$41.44	3.504%	$42.8921	$42.89	$42.90	$42.90
Purchase #4	$159.98	13.307%	$181.2685	$181.27	$181.25	$181.30
Purchase #5	$214.69	5.557%	$226.6203	$226.62	$226.60	$226.60
Purchase #6	$174.32	3.504%	$180.4282	$180.43	$180.45	$180.40
Purchase #7	$44.27	3.626%	$45.8752	$45.88	$45.90	$45.90
7 purchase totals =	$760.73		$816.0909	$816.10	$816.15	$816.10