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	$56.91	8.478%	$61.7348	$61.73	$61.75	$61.70
Purchase #2	$163.80	10.231%	$180.5584	$180.56	$180.55	$180.60
Purchase #3	$43.93	3.659%	$45.5374	$45.54	$45.55	$45.50
Purchase #4	$246.70	12.780%	$278.2283	$278.23	$278.25	$278.20
Purchase #5	$105.51	5.222%	$111.0197	$111.02	$111.00	$111.00
Purchase #6	$117.74	12.871%	$132.8943	$132.89	$132.90	$132.90
Purchase #7	$121.72	3.256%	$125.6832	$125.68	$125.70	$125.70
7 purchase totals =	$856.31		$935.6561	$935.65	$935.70	$935.60