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	$138.86	9.323%	$151.8059	$151.81	$151.80	$151.80
Purchase #2	$71.69	9.182%	$78.2726	$78.27	$78.25	$78.30
Purchase #3	$142.57	4.363%	$148.7903	$148.79	$148.80	$148.80
Purchase #4	$197.44	5.330%	$207.9636	$207.96	$207.95	$208.00
Purchase #5	$14.76	7.593%	$15.8807	$15.88	$15.90	$15.90
Purchase #6	$143.58	5.210%	$151.0605	$151.06	$151.05	$151.10
Purchase #7	$173.93	10.232%	$191.7265	$191.73	$191.75	$191.70
7 purchase totals =	$882.83		$945.5001	$945.50	$945.50	$945.60