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	$60.25	8.141%	$65.155	$65.16	$65.15	$65.20
Purchase #2	$176.92	11.235%	$196.797	$196.80	$196.80	$196.80
Purchase #3	$219.84	12.854%	$248.0982	$248.10	$248.10	$248.10
Purchase #4	$59.70	4.750%	$62.5358	$62.54	$62.55	$62.50
Purchase #5	$183.51	13.492%	$208.2692	$208.27	$208.25	$208.30
Purchase #6	$40.46	4.523%	$42.29	$42.29	$42.30	$42.30
Purchase #7	$182.67	7.122%	$195.6798	$195.68	$195.70	$195.70
7 purchase totals =	$923.35		$1,018.8250	$1,018.84	$1,018.85	$1,018.90