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	$22.81	10.353%	$25.1715	$25.17	$25.15	$25.20
Purchase #2	$95.73	12.722%	$107.9088	$107.91	$107.90	$107.90
Purchase #3	$156.59	10.206%	$172.5716	$172.57	$172.55	$172.60
Purchase #4	$162.29	10.276%	$178.9669	$178.97	$178.95	$179.00
Purchase #5	$111.51	10.373%	$123.0769	$123.08	$123.10	$123.10
Purchase #6	$149.94	9.528%	$164.2263	$164.23	$164.25	$164.20
Purchase #7	$230.79	8.127%	$249.5463	$249.55	$249.55	$249.50
7 purchase totals =	$929.66		$1,021.4683	$1,021.48	$1,021.45	$1,021.50