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	$119.95	9.329%	$131.1401	$131.14	$131.15	$131.10
Purchase #2	$179.46	10.758%	$198.7663	$198.77	$198.75	$198.80
Purchase #3	$78.45	11.204%	$87.2395	$87.24	$87.25	$87.20
Purchase #4	$88.95	13.384%	$100.8551	$100.86	$100.85	$100.90
Purchase #5	$158.86	12.389%	$178.5412	$178.54	$178.55	$178.50
Purchase #6	$222.47	11.555%	$248.1764	$248.18	$248.20	$248.20
Purchase #7	$125.65	8.801%	$136.7085	$136.71	$136.70	$136.70
7 purchase totals =	$973.79		$1,081.4271	$1,081.44	$1,081.45	$1,081.40