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	$60.54	4.768%	$63.4265	$63.43	$63.45	$63.40
Purchase #2	$40.58	5.624%	$42.8622	$42.86	$42.85	$42.90
Purchase #3	$235.86	10.761%	$261.2409	$261.24	$261.25	$261.20
Purchase #4	$190.56	6.324%	$202.611	$202.61	$202.60	$202.60
Purchase #5	$145.56	6.546%	$155.0884	$155.09	$155.10	$155.10
Purchase #6	$200.77	13.165%	$227.2014	$227.20	$227.20	$227.20
Purchase #7	$128.67	4.489%	$134.446	$134.45	$134.45	$134.40
7 purchase totals =	$1,002.54		$1,086.8764	$1,086.88	$1,086.90	$1,086.80