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	$55.31	7.680%	$59.5578	$59.56	$59.55	$59.60
Purchase #2	$99.41	9.605%	$108.9583	$108.96	$108.95	$109.00
Purchase #3	$136.57	5.678%	$144.3244	$144.32	$144.30	$144.30
Purchase #4	$142.65	10.563%	$157.7181	$157.72	$157.70	$157.70
Purchase #5	$180.52	8.722%	$196.265	$196.27	$196.25	$196.30
Purchase #6	$203.79	5.144%	$214.273	$214.27	$214.25	$214.30
Purchase #7	$83.75	7.265%	$89.8344	$89.83	$89.85	$89.80
7 purchase totals =	$902.00		$970.9310	$970.93	$970.85	$971.00