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	$93.58	12.360%	$105.1465	$105.15	$105.15	$105.10
Purchase #2	$229.58	13.501%	$260.5756	$260.58	$260.60	$260.60
Purchase #3	$152.85	8.621%	$166.0272	$166.03	$166.05	$166.00
Purchase #4	$217.76	10.404%	$240.4158	$240.42	$240.40	$240.40
Purchase #5	$37.83	13.599%	$42.9745	$42.97	$42.95	$43.00
Purchase #6	$5.28	5.156%	$5.5522	$5.55	$5.55	$5.60
Purchase #7	$210.89	13.646%	$239.668	$239.67	$239.65	$239.70
7 purchase totals =	$947.77		$1,060.3598	$1,060.37	$1,060.35	$1,060.40