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	$111.38	12.471%	$125.2702	$125.27	$125.25	$125.30
Purchase #2	$227.88	12.167%	$255.6062	$255.61	$255.60	$255.60
Purchase #3	$223.71	7.291%	$240.0207	$240.02	$240.00	$240.00
Purchase #4	$242.54	12.150%	$272.0086	$272.01	$272.00	$272.00
Purchase #5	$186.31	3.293%	$192.4452	$192.45	$192.45	$192.40
Purchase #6	$154.40	10.801%	$171.0767	$171.08	$171.10	$171.10
Purchase #7	$68.51	11.785%	$76.5839	$76.58	$76.60	$76.60
7 purchase totals =	$1,214.73		$1,333.0115	$1,333.02	$1,333.00	$1,333.00