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	$174.79	9.866%	$192.0348	$192.03	$192.05	$192.00
Purchase #2	$168.43	13.347%	$190.9104	$190.91	$190.90	$190.90
Purchase #3	$158.37	6.556%	$168.7527	$168.75	$168.75	$168.80
Purchase #4	$155.29	7.374%	$166.7411	$166.74	$166.75	$166.70
Purchase #5	$39.37	8.109%	$42.5625	$42.56	$42.55	$42.60
Purchase #6	$145.70	12.188%	$163.4579	$163.46	$163.45	$163.50
Purchase #7	$30.57	6.190%	$32.4623	$32.46	$32.45	$32.50
7 purchase totals =	$872.52		$956.9217	$956.91	$956.90	$957.00