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	$49.35	12.542%	$55.5395	$55.54	$55.55	$55.50
Purchase #2	$243.34	7.134%	$260.6999	$260.70	$260.70	$260.70
Purchase #3	$119.64	10.853%	$132.6245	$132.62	$132.60	$132.60
Purchase #4	$165.57	4.137%	$172.4196	$172.42	$172.40	$172.40
Purchase #5	$159.37	3.389%	$164.771	$164.77	$164.75	$164.80
Purchase #6	$77.44	6.544%	$82.5077	$82.51	$82.50	$82.50
Purchase #7	$245.25	7.359%	$263.2979	$263.30	$263.30	$263.30
7 purchase totals =	$1,059.96		$1,131.8601	$1,131.86	$1,131.80	$1,131.80