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	$177.94	12.549%	$200.2697	$200.27	$200.25	$200.30
Purchase #2	$158.70	6.260%	$168.6346	$168.63	$168.65	$168.60
Purchase #3	$174.28	9.375%	$190.6188	$190.62	$190.60	$190.60
Purchase #4	$59.82	12.704%	$67.4195	$67.42	$67.40	$67.40
Purchase #5	$185.75	13.318%	$210.4882	$210.49	$210.50	$210.50
Purchase #6	$193.72	6.198%	$205.7268	$205.73	$205.75	$205.70
Purchase #7	$47.83	8.188%	$51.7463	$51.75	$51.75	$51.70
7 purchase totals =	$998.04		$1,094.9039	$1,094.91	$1,094.90	$1,094.80