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	$179.55	10.526%	$198.4494	$198.45	$198.45	$198.40
Purchase #2	$13.44	3.501%	$13.9105	$13.91	$13.90	$13.90
Purchase #3	$105.37	10.538%	$116.4739	$116.47	$116.45	$116.50
Purchase #4	$120.90	10.682%	$133.8145	$133.81	$133.80	$133.80
Purchase #5	$70.86	3.273%	$73.1792	$73.18	$73.20	$73.20
Purchase #6	$25.78	5.644%	$27.235	$27.24	$27.25	$27.20
Purchase #7	$176.71	5.188%	$185.8777	$185.88	$185.90	$185.90
7 purchase totals =	$692.61		$748.9402	$748.94	$748.95	$748.90