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	$229.33	12.228%	$257.3725	$257.37	$257.35	$257.40
Purchase #2	$207.53	7.749%	$223.6115	$223.61	$223.60	$223.60
Purchase #3	$150.26	3.603%	$155.6739	$155.67	$155.65	$155.70
Purchase #4	$234.62	11.478%	$261.5497	$261.55	$261.55	$261.50
Purchase #5	$44.61	3.517%	$46.1789	$46.18	$46.20	$46.20
Purchase #6	$100.45	11.310%	$111.8109	$111.81	$111.80	$111.80
Purchase #7	$98.59	6.137%	$104.6405	$104.64	$104.65	$104.60
7 purchase totals =	$1,065.39		$1,160.8379	$1,160.83	$1,160.80	$1,160.80