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	$241.85	11.169%	$268.8622	$268.86	$268.85	$268.90
Purchase #2	$216.99	7.247%	$232.7153	$232.72	$232.70	$232.70
Purchase #3	$153.67	5.679%	$162.3969	$162.40	$162.40	$162.40
Purchase #4	$36.85	4.109%	$38.3642	$38.36	$38.35	$38.40
Purchase #5	$31.78	5.708%	$33.594	$33.59	$33.60	$33.60
Purchase #6	$59.70	7.732%	$64.316	$64.32	$64.30	$64.30
Purchase #7	$127.31	12.212%	$142.8571	$142.86	$142.85	$142.90
7 purchase totals =	$868.15		$943.1057	$943.11	$943.05	$943.20