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	$144.61	12.291%	$162.384	$162.38	$162.40	$162.40
Purchase #2	$152.68	10.425%	$168.5969	$168.60	$168.60	$168.60
Purchase #3	$173.25	12.338%	$194.6256	$194.63	$194.65	$194.60
Purchase #4	$40.28	10.630%	$44.5618	$44.56	$44.55	$44.60
Purchase #5	$53.71	5.227%	$56.5174	$56.52	$56.50	$56.50
Purchase #6	$93.79	6.506%	$99.892	$99.89	$99.90	$99.90
Purchase #7	$136.28	6.126%	$144.6285	$144.63	$144.65	$144.60
7 purchase totals =	$794.60		$871.2062	$871.21	$871.25	$871.20