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	$52.40	6.503%	$55.8076	$55.81	$55.80	$55.80
Purchase #2	$250.83	5.393%	$264.3573	$264.36	$264.35	$264.40
Purchase #3	$172.32	13.840%	$196.1691	$196.17	$196.15	$196.20
Purchase #4	$119.88	10.434%	$132.3883	$132.39	$132.40	$132.40
Purchase #5	$194.93	13.497%	$221.2397	$221.24	$221.25	$221.20
Purchase #6	$219.37	9.556%	$240.333	$240.33	$240.35	$240.30
Purchase #7	$120.80	5.627%	$127.5974	$127.60	$127.60	$127.60
7 purchase totals =	$1,130.53		$1,237.8924	$1,237.90	$1,237.90	$1,237.90