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	$120.27	11.210%	$133.7523	$133.75	$133.75	$133.80
Purchase #2	$196.75	6.188%	$208.9249	$208.92	$208.90	$208.90
Purchase #3	$179.51	8.342%	$194.4847	$194.48	$194.50	$194.50
Purchase #4	$110.94	12.382%	$124.6766	$124.68	$124.70	$124.70
Purchase #5	$222.44	5.443%	$234.5474	$234.55	$234.55	$234.50
Purchase #6	$149.82	12.472%	$168.5056	$168.51	$168.50	$168.50
Purchase #7	$20.59	6.739%	$21.9776	$21.98	$22.00	$22.00
7 purchase totals =	$1,000.32		$1,086.8691	$1,086.87	$1,086.90	$1,086.90