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	$137.93	4.376%	$143.9658	$143.97	$143.95	$144.00
Purchase #2	$175.78	8.314%	$190.3943	$190.39	$190.40	$190.40
Purchase #3	$230.31	5.870%	$243.8292	$243.83	$243.85	$243.80
Purchase #4	$66.96	6.406%	$71.2495	$71.25	$71.25	$71.20
Purchase #5	$168.74	13.628%	$191.7359	$191.74	$191.75	$191.70
Purchase #6	$224.86	7.296%	$241.2658	$241.27	$241.25	$241.30
Purchase #7	$33.28	10.828%	$36.8836	$36.88	$36.90	$36.90
7 purchase totals =	$1,037.86		$1,119.3241	$1,119.33	$1,119.35	$1,119.30