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	$89.98	9.770%	$98.771	$98.77	$98.75	$98.80
Purchase #2	$241.52	3.776%	$250.6398	$250.64	$250.65	$250.60
Purchase #3	$40.89	5.667%	$43.2072	$43.21	$43.20	$43.20
Purchase #4	$105.34	5.484%	$111.1168	$111.12	$111.10	$111.10
Purchase #5	$153.69	9.252%	$167.9094	$167.91	$167.90	$167.90
Purchase #6	$179.33	9.519%	$196.4004	$196.40	$196.40	$196.40
Purchase #7	$136.43	8.845%	$148.4972	$148.50	$148.50	$148.50
7 purchase totals =	$947.18		$1,016.5418	$1,016.55	$1,016.50	$1,016.50