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	$149.40	11.370%	$166.3868	$166.39	$166.40	$166.40
Purchase #2	$38.40	11.837%	$42.9454	$42.95	$42.95	$42.90
Purchase #3	$196.28	8.779%	$213.5114	$213.51	$213.50	$213.50
Purchase #4	$227.58	6.212%	$241.7173	$241.72	$241.70	$241.70
Purchase #5	$78.48	6.423%	$83.5208	$83.52	$83.50	$83.50
Purchase #6	$250.33	7.237%	$268.4464	$268.45	$268.45	$268.40
Purchase #7	$205.57	7.593%	$221.1789	$221.18	$221.20	$221.20
7 purchase totals =	$1,146.04		$1,237.7070	$1,237.72	$1,237.70	$1,237.60