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	$119.93	10.813%	$132.898	$132.90	$132.90	$132.90
Purchase #2	$166.58	13.396%	$188.8951	$188.90	$188.90	$188.90
Purchase #3	$88.74	12.282%	$99.639	$99.64	$99.65	$99.60
Purchase #4	$239.87	7.787%	$258.5487	$258.55	$258.55	$258.50
Purchase #5	$7.59	4.115%	$7.9023	$7.90	$7.90	$7.90
Purchase #6	$197.35	4.181%	$205.6012	$205.60	$205.60	$205.60
Purchase #7	$167.39	3.629%	$173.4646	$173.46	$173.45	$173.50
7 purchase totals =	$987.45		$1,066.9489	$1,066.95	$1,066.95	$1,066.90