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	$90.43	7.109%	$96.8587	$96.86	$96.85	$96.90
Purchase #2	$204.65	7.357%	$219.7061	$219.71	$219.70	$219.70
Purchase #3	$67.82	13.336%	$76.8645	$76.86	$76.85	$76.90
Purchase #4	$151.85	11.243%	$168.9225	$168.92	$168.90	$168.90
Purchase #5	$218.29	4.169%	$227.3905	$227.39	$227.40	$227.40
Purchase #6	$73.77	7.606%	$79.3809	$79.38	$79.40	$79.40
Purchase #7	$208.95	10.480%	$230.848	$230.85	$230.85	$230.80
7 purchase totals =	$1,015.76		$1,099.9712	$1,099.97	$1,099.95	$1,100.00