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	$118.98	7.493%	$127.8952	$127.90	$127.90	$127.90
Purchase #2	$20.66	4.786%	$21.6488	$21.65	$21.65	$21.60
Purchase #3	$222.58	8.604%	$241.7308	$241.73	$241.75	$241.70
Purchase #4	$154.27	4.287%	$160.8836	$160.88	$160.90	$160.90
Purchase #5	$41.36	7.248%	$44.3578	$44.36	$44.35	$44.40
Purchase #6	$54.61	7.208%	$58.5463	$58.55	$58.55	$58.50
Purchase #7	$10.34	4.418%	$10.7968	$10.80	$10.80	$10.80
7 purchase totals =	$622.80		$665.8593	$665.87	$665.90	$665.80