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	$51.89	5.607%	$54.7995	$54.80	$54.80	$54.80
Purchase #2	$198.49	3.167%	$204.7762	$204.78	$204.80	$204.80
Purchase #3	$99.87	11.184%	$111.0395	$111.04	$111.05	$111.00
Purchase #4	$136.73	11.849%	$152.9311	$152.93	$152.95	$152.90
Purchase #5	$54.66	7.375%	$58.6912	$58.69	$58.70	$58.70
Purchase #6	$185.96	5.746%	$196.6453	$196.65	$196.65	$196.60
Purchase #7	$183.93	13.446%	$208.6612	$208.66	$208.65	$208.70
7 purchase totals =	$911.53		$987.5440	$987.55	$987.60	$987.50