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	$194.84	9.120%	$212.6094	$212.61	$212.60	$212.60
Purchase #2	$115.45	6.352%	$122.7834	$122.78	$122.80	$122.80
Purchase #3	$162.77	4.748%	$170.4983	$170.50	$170.50	$170.50
Purchase #4	$238.52	5.192%	$250.904	$250.90	$250.90	$250.90
Purchase #5	$48.96	12.119%	$54.8935	$54.89	$54.90	$54.90
Purchase #6	$161.48	7.413%	$173.4505	$173.45	$173.45	$173.50
Purchase #7	$92.81	5.863%	$98.2515	$98.25	$98.25	$98.30
7 purchase totals =	$1,014.83		$1,083.3906	$1,083.38	$1,083.40	$1,083.50