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	$168.78	4.156%	$175.7945	$175.79	$175.80	$175.80
Purchase #2	$181.80	8.209%	$196.724	$196.72	$196.70	$196.70
Purchase #3	$75.91	3.525%	$78.5858	$78.59	$78.60	$78.60
Purchase #4	$79.89	6.860%	$85.3705	$85.37	$85.35	$85.40
Purchase #5	$144.92	6.578%	$154.4528	$154.45	$154.45	$154.50
Purchase #6	$132.29	10.314%	$145.9344	$145.93	$145.95	$145.90
Purchase #7	$45.90	4.421%	$47.9292	$47.93	$47.95	$47.90
7 purchase totals =	$829.49		$884.7912	$884.78	$884.80	$884.80