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	$53.94	8.680%	$58.622	$58.62	$58.60	$58.60
Purchase #2	$90.80	9.610%	$99.5259	$99.53	$99.55	$99.50
Purchase #3	$69.74	10.154%	$76.8214	$76.82	$76.80	$76.80
Purchase #4	$150.29	6.649%	$160.2828	$160.28	$160.30	$160.30
Purchase #5	$20.25	8.315%	$21.9338	$21.93	$21.95	$21.90
Purchase #6	$13.93	6.663%	$14.8582	$14.86	$14.85	$14.90
Purchase #7	$248.50	10.230%	$273.9216	$273.92	$273.90	$273.90
7 purchase totals =	$647.45		$705.9657	$705.96	$705.95	$705.90