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	$35.57	4.273%	$37.0899	$37.09	$37.10	$37.10
Purchase #2	$72.85	12.636%	$82.0553	$82.06	$82.05	$82.10
Purchase #3	$132.65	13.688%	$150.8071	$150.81	$150.80	$150.80
Purchase #4	$72.51	5.864%	$76.762	$76.76	$76.75	$76.80
Purchase #5	$125.99	5.233%	$132.5831	$132.58	$132.60	$132.60
Purchase #6	$41.29	7.862%	$44.5362	$44.54	$44.55	$44.50
Purchase #7	$98.77	3.161%	$101.8921	$101.89	$101.90	$101.90
7 purchase totals =	$579.63		$625.7257	$625.73	$625.75	$625.80