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	$80.93	9.109%	$88.3019	$88.30	$88.30	$88.30
Purchase #2	$71.57	9.750%	$78.5481	$78.55	$78.55	$78.50
Purchase #3	$49.59	9.697%	$54.3987	$54.40	$54.40	$54.40
Purchase #4	$16.86	11.367%	$18.7765	$18.78	$18.80	$18.80
Purchase #5	$8.48	13.476%	$9.6228	$9.62	$9.60	$9.60
Purchase #6	$65.31	3.411%	$67.5377	$67.54	$67.55	$67.50
Purchase #7	$13.71	13.538%	$15.5661	$15.57	$15.55	$15.60
7 purchase totals =	$306.45		$332.7518	$332.76	$332.75	$332.70