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	$34.53	4.862%	$36.2088	$36.21	$36.20	$36.20
Purchase #2	$239.46	7.736%	$257.9846	$257.98	$258.00	$258.00
Purchase #3	$163.35	10.775%	$180.951	$180.95	$180.95	$181.00
Purchase #4	$107.94	9.373%	$118.0572	$118.06	$118.05	$118.10
Purchase #5	$173.77	9.543%	$190.3529	$190.35	$190.35	$190.40
Purchase #6	$179.56	6.806%	$191.7809	$191.78	$191.80	$191.80
Purchase #7	$101.71	9.173%	$111.0399	$111.04	$111.05	$111.00
7 purchase totals =	$1,000.32		$1,086.3753	$1,086.37	$1,086.40	$1,086.50