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	$215.28	11.807%	$240.6981	$240.70	$240.70	$240.70
Purchase #2	$192.51	10.431%	$212.5907	$212.59	$212.60	$212.60
Purchase #3	$229.56	5.527%	$242.2478	$242.25	$242.25	$242.20
Purchase #4	$155.71	5.632%	$164.4796	$164.48	$164.50	$164.50
Purchase #5	$57.50	3.841%	$59.7086	$59.71	$59.70	$59.70
Purchase #6	$72.89	7.748%	$78.5375	$78.54	$78.55	$78.50
Purchase #7	$247.75	10.542%	$273.8678	$273.87	$273.85	$273.90
7 purchase totals =	$1,171.20		$1,272.1301	$1,272.14	$1,272.15	$1,272.10