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	$113.78	4.788%	$119.2278	$119.23	$119.25	$119.20
Purchase #2	$223.40	8.229%	$241.7836	$241.78	$241.80	$241.80
Purchase #3	$75.72	3.356%	$78.2612	$78.26	$78.25	$78.30
Purchase #4	$206.73	7.685%	$222.6172	$222.62	$222.60	$222.60
Purchase #5	$50.58	3.723%	$52.4631	$52.46	$52.45	$52.50
Purchase #6	$245.77	13.809%	$279.7084	$279.71	$279.70	$279.70
Purchase #7	$224.89	5.344%	$236.9081	$236.91	$236.90	$236.90
7 purchase totals =	$1,140.87		$1,230.9694	$1,230.97	$1,230.95	$1,231.00