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	$71.34	9.688%	$78.2514	$78.25	$78.25	$78.30
Purchase #2	$241.69	10.293%	$266.5672	$266.57	$266.55	$266.60
Purchase #3	$153.93	5.338%	$162.1468	$162.15	$162.15	$162.10
Purchase #4	$191.28	7.185%	$205.0235	$205.02	$205.00	$205.00
Purchase #5	$113.90	11.396%	$126.88	$126.88	$126.90	$126.90
Purchase #6	$139.58	4.278%	$145.5512	$145.55	$145.55	$145.60
Purchase #7	$229.36	5.475%	$241.9175	$241.92	$241.90	$241.90
7 purchase totals =	$1,141.08		$1,226.3376	$1,226.34	$1,226.30	$1,226.40