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	$159.41	9.110%	$173.9323	$173.93	$173.95	$173.90
Purchase #2	$215.44	10.719%	$238.533	$238.53	$238.55	$238.50
Purchase #3	$136.49	4.689%	$142.89	$142.89	$142.90	$142.90
Purchase #4	$220.94	6.244%	$234.7355	$234.74	$234.75	$234.70
Purchase #5	$173.71	10.467%	$191.8922	$191.89	$191.90	$191.90
Purchase #6	$77.67	6.841%	$82.9834	$82.98	$83.00	$83.00
Purchase #7	$203.79	6.415%	$216.8631	$216.86	$216.85	$216.90
7 purchase totals =	$1,187.45		$1,281.8295	$1,281.82	$1,281.90	$1,281.80