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	$134.85	9.382%	$147.5016	$147.50	$147.50	$147.50
Purchase #2	$19.27	6.768%	$20.5742	$20.57	$20.55	$20.60
Purchase #3	$100.80	11.820%	$112.7146	$112.71	$112.70	$112.70
Purchase #4	$181.33	8.485%	$196.7159	$196.72	$196.70	$196.70
Purchase #5	$29.53	13.598%	$33.5455	$33.55	$33.55	$33.50
Purchase #6	$116.97	5.236%	$123.0945	$123.09	$123.10	$123.10
Purchase #7	$227.68	3.117%	$234.7768	$234.78	$234.80	$234.80
7 purchase totals =	$810.43		$868.9231	$868.92	$868.90	$868.90