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	$51.90	4.339%	$54.1519	$54.15	$54.15	$54.20
Purchase #2	$212.37	4.361%	$221.6315	$221.63	$221.65	$221.60
Purchase #3	$164.62	7.438%	$176.8644	$176.86	$176.85	$176.90
Purchase #4	$78.63	8.547%	$85.3505	$85.35	$85.35	$85.40
Purchase #5	$203.68	4.285%	$212.4077	$212.41	$212.40	$212.40
Purchase #6	$32.85	13.854%	$37.401	$37.40	$37.40	$37.40
Purchase #7	$170.60	5.318%	$179.6725	$179.67	$179.65	$179.70
7 purchase totals =	$914.65		$967.4795	$967.47	$967.45	$967.60