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	$248.48	5.782%	$262.8471	$262.85	$262.85	$262.80
Purchase #2	$167.86	3.844%	$174.3125	$174.31	$174.30	$174.30
Purchase #3	$128.25	10.381%	$141.5636	$141.56	$141.55	$141.60
Purchase #4	$150.29	11.227%	$167.1631	$167.16	$167.15	$167.20
Purchase #5	$153.81	6.556%	$163.8938	$163.89	$163.90	$163.90
Purchase #6	$48.57	12.369%	$54.5776	$54.58	$54.60	$54.60
Purchase #7	$160.57	11.839%	$179.5799	$179.58	$179.60	$179.60
7 purchase totals =	$1,057.83		$1,143.9376	$1,143.93	$1,143.95	$1,144.00