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	$182.59	11.332%	$203.2811	$203.28	$203.30	$203.30
Purchase #2	$131.93	10.297%	$145.5148	$145.51	$145.50	$145.50
Purchase #3	$91.65	8.186%	$99.1525	$99.15	$99.15	$99.20
Purchase #4	$75.31	4.166%	$78.4474	$78.45	$78.45	$78.40
Purchase #5	$172.56	13.611%	$196.0471	$196.05	$196.05	$196.00
Purchase #6	$170.44	10.138%	$187.7192	$187.72	$187.70	$187.70
Purchase #7	$228.79	8.648%	$248.5758	$248.58	$248.60	$248.60
7 purchase totals =	$1,053.27		$1,158.7379	$1,158.74	$1,158.75	$1,158.70