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	$113.97	10.664%	$126.1238	$126.12	$126.10	$126.10
Purchase #2	$78.89	12.692%	$88.9027	$88.90	$88.90	$88.90
Purchase #3	$223.60	10.352%	$246.7471	$246.75	$246.75	$246.70
Purchase #4	$10.82	6.481%	$11.5212	$11.52	$11.50	$11.50
Purchase #5	$110.32	9.711%	$121.0332	$121.03	$121.05	$121.00
Purchase #6	$17.84	12.792%	$20.1221	$20.12	$20.10	$20.10
Purchase #7	$48.37	9.229%	$52.8341	$52.83	$52.85	$52.80
7 purchase totals =	$603.81		$667.2842	$667.27	$667.25	$667.10