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	$160.93	3.116%	$165.9446	$165.94	$165.95	$165.90
Purchase #2	$91.48	8.629%	$99.3738	$99.37	$99.35	$99.40
Purchase #3	$187.84	6.790%	$200.5943	$200.59	$200.60	$200.60
Purchase #4	$62.57	10.684%	$69.255	$69.26	$69.25	$69.30
Purchase #5	$214.86	10.382%	$237.1668	$237.17	$237.15	$237.20
Purchase #6	$168.76	9.605%	$184.9694	$184.97	$184.95	$185.00
Purchase #7	$198.67	13.561%	$225.6116	$225.61	$225.60	$225.60
7 purchase totals =	$1,085.11		$1,182.9155	$1,182.91	$1,182.85	$1,183.00