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	$137.80	13.542%	$156.4609	$156.46	$156.45	$156.50
Purchase #2	$10.89	5.266%	$11.4635	$11.46	$11.45	$11.50
Purchase #3	$168.41	12.750%	$189.8823	$189.88	$189.90	$189.90
Purchase #4	$202.39	9.535%	$221.6879	$221.69	$221.70	$221.70
Purchase #5	$67.82	13.786%	$77.1697	$77.17	$77.15	$77.20
Purchase #6	$215.32	10.367%	$237.6422	$237.64	$237.65	$237.60
Purchase #7	$143.92	11.577%	$160.5816	$160.58	$160.60	$160.60
7 purchase totals =	$946.55		$1,054.8881	$1,054.88	$1,054.90	$1,055.00