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	$11.96	4.169%	$12.4586	$12.46	$12.45	$12.50
Purchase #2	$46.72	4.785%	$48.9556	$48.96	$48.95	$49.00
Purchase #3	$238.26	13.675%	$270.8421	$270.84	$270.85	$270.80
Purchase #4	$59.75	9.751%	$65.5762	$65.58	$65.60	$65.60
Purchase #5	$71.88	12.150%	$80.6134	$80.61	$80.60	$80.60
Purchase #6	$225.59	5.324%	$237.6004	$237.60	$237.60	$237.60
Purchase #7	$202.60	13.461%	$229.872	$229.87	$229.85	$229.90
7 purchase totals =	$856.76		$945.9183	$945.92	$945.90	$946.00