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	$80.94	6.151%	$85.9186	$85.92	$85.90	$85.90
Purchase #2	$225.89	10.607%	$249.8502	$249.85	$249.85	$249.90
Purchase #3	$219.84	13.229%	$248.9226	$248.92	$248.90	$248.90
Purchase #4	$132.33	3.297%	$136.6929	$136.69	$136.70	$136.70
Purchase #5	$176.78	8.367%	$191.5712	$191.57	$191.55	$191.60
Purchase #6	$171.28	3.857%	$177.8863	$177.89	$177.90	$177.90
Purchase #7	$154.90	12.149%	$173.7188	$173.72	$173.70	$173.70
7 purchase totals =	$1,161.96		$1,264.5606	$1,264.56	$1,264.50	$1,264.60