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	$9.74	9.833%	$10.6977	$10.70	$10.70	$10.70
Purchase #2	$203.26	6.526%	$216.5247	$216.52	$216.50	$216.50
Purchase #3	$148.58	11.752%	$166.0411	$166.04	$166.05	$166.00
Purchase #4	$94.27	10.139%	$103.828	$103.83	$103.85	$103.80
Purchase #5	$183.88	13.240%	$208.2257	$208.23	$208.25	$208.20
Purchase #6	$83.46	7.242%	$89.5042	$89.50	$89.50	$89.50
Purchase #7	$94.45	6.263%	$100.3654	$100.37	$100.35	$100.40
7 purchase totals =	$817.64		$895.1868	$895.19	$895.20	$895.10