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	$87.58	7.468%	$94.1205	$94.12	$94.10	$94.10
Purchase #2	$100.84	3.445%	$104.3139	$104.31	$104.30	$104.30
Purchase #3	$225.70	3.380%	$233.3287	$233.33	$233.35	$233.30
Purchase #4	$30.84	11.624%	$34.4248	$34.42	$34.40	$34.40
Purchase #5	$41.81	5.209%	$43.9879	$43.99	$44.00	$44.00
Purchase #6	$214.46	11.386%	$238.8784	$238.88	$238.90	$238.90
Purchase #7	$174.67	12.595%	$196.6697	$196.67	$196.65	$196.70
7 purchase totals =	$875.90		$945.7239	$945.72	$945.70	$945.70