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	$39.55	7.696%	$42.5938	$42.59	$42.60	$42.60
Purchase #2	$213.67	9.396%	$233.7464	$233.75	$233.75	$233.70
Purchase #3	$97.61	13.805%	$111.0851	$111.09	$111.10	$111.10
Purchase #4	$107.87	9.772%	$118.4111	$118.41	$118.40	$118.40
Purchase #5	$146.46	8.601%	$159.057	$159.06	$159.05	$159.10
Purchase #6	$208.63	5.617%	$220.3487	$220.35	$220.35	$220.30
Purchase #7	$111.90	11.508%	$124.7775	$124.78	$124.80	$124.80
7 purchase totals =	$925.69		$1,010.0196	$1,010.03	$1,010.05	$1,010.00