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	$40.89	4.447%	$42.7084	$42.71	$42.70	$42.70
Purchase #2	$238.88	9.801%	$262.2926	$262.29	$262.30	$262.30
Purchase #3	$126.78	5.746%	$134.0648	$134.06	$134.05	$134.10
Purchase #4	$53.56	4.179%	$55.7983	$55.80	$55.80	$55.80
Purchase #5	$52.73	10.648%	$58.3447	$58.34	$58.35	$58.30
Purchase #6	$237.50	7.193%	$254.5834	$254.58	$254.60	$254.60
Purchase #7	$222.78	7.546%	$239.591	$239.59	$239.60	$239.60
7 purchase totals =	$973.12		$1,047.3832	$1,047.37	$1,047.40	$1,047.40