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	$245.58	12.259%	$275.6857	$275.69	$275.70	$275.70
Purchase #2	$152.72	7.772%	$164.5894	$164.59	$164.60	$164.60
Purchase #3	$161.81	3.571%	$167.5882	$167.59	$167.60	$167.60
Purchase #4	$111.60	10.425%	$123.2343	$123.23	$123.25	$123.20
Purchase #5	$82.43	5.514%	$86.9752	$86.98	$87.00	$87.00
Purchase #6	$147.36	11.261%	$163.9542	$163.95	$163.95	$164.00
Purchase #7	$37.72	4.240%	$39.3193	$39.32	$39.30	$39.30
7 purchase totals =	$939.22		$1,021.3463	$1,021.35	$1,021.40	$1,021.40