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	$170.39	11.540%	$190.053	$190.05	$190.05	$190.10
Purchase #2	$35.40	5.750%	$37.4355	$37.44	$37.45	$37.40
Purchase #3	$78.54	8.872%	$85.5081	$85.51	$85.50	$85.50
Purchase #4	$39.54	8.614%	$42.946	$42.95	$42.95	$42.90
Purchase #5	$151.40	8.236%	$163.8693	$163.87	$163.85	$163.90
Purchase #6	$168.36	3.525%	$174.2947	$174.29	$174.30	$174.30
Purchase #7	$210.52	13.757%	$239.4812	$239.48	$239.50	$239.50
7 purchase totals =	$854.15		$933.5878	$933.59	$933.60	$933.60