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	$41.45	5.235%	$43.6199	$43.62	$43.60	$43.60
Purchase #2	$92.83	8.509%	$100.7289	$100.73	$100.75	$100.70
Purchase #3	$109.63	7.649%	$118.0156	$118.02	$118.00	$118.00
Purchase #4	$187.31	10.362%	$206.7191	$206.72	$206.70	$206.70
Purchase #5	$20.47	4.786%	$21.4497	$21.45	$21.45	$21.40
Purchase #6	$200.34	8.130%	$216.6276	$216.63	$216.65	$216.60
Purchase #7	$99.34	13.635%	$112.885	$112.89	$112.90	$112.90
7 purchase totals =	$751.37		$820.0458	$820.06	$820.05	$819.90