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	$208.67	6.627%	$222.4986	$222.50	$222.50	$222.50
Purchase #2	$69.95	3.773%	$72.5892	$72.59	$72.60	$72.60
Purchase #3	$36.80	10.448%	$40.6449	$40.64	$40.65	$40.60
Purchase #4	$78.36	9.354%	$85.6898	$85.69	$85.70	$85.70
Purchase #5	$148.44	7.726%	$159.9085	$159.91	$159.90	$159.90
Purchase #6	$96.63	12.167%	$108.387	$108.39	$108.40	$108.40
Purchase #7	$11.69	13.416%	$13.2583	$13.26	$13.25	$13.30
7 purchase totals =	$650.54		$702.9763	$702.98	$703.00	$703.00