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	$187.75	4.527%	$196.2494	$196.25	$196.25	$196.20
Purchase #2	$75.36	9.540%	$82.5493	$82.55	$82.55	$82.50
Purchase #3	$102.43	8.691%	$111.3322	$111.33	$111.35	$111.30
Purchase #4	$218.68	7.611%	$235.3237	$235.32	$235.30	$235.30
Purchase #5	$81.98	6.842%	$87.5891	$87.59	$87.60	$87.60
Purchase #6	$191.81	7.786%	$206.7443	$206.74	$206.75	$206.70
Purchase #7	$89.62	10.649%	$99.1636	$99.16	$99.15	$99.20
7 purchase totals =	$947.63		$1,018.9516	$1,018.94	$1,018.95	$1,018.80