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	$232.81	6.719%	$248.4525	$248.45	$248.45	$248.50
Purchase #2	$196.87	4.573%	$205.8729	$205.87	$205.85	$205.90
Purchase #3	$182.87	9.453%	$200.1567	$200.16	$200.15	$200.20
Purchase #4	$99.55	4.561%	$104.0905	$104.09	$104.10	$104.10
Purchase #5	$103.59	11.849%	$115.8644	$115.86	$115.85	$115.90
Purchase #6	$16.50	9.414%	$18.0533	$18.05	$18.05	$18.10
Purchase #7	$131.59	7.458%	$141.404	$141.40	$141.40	$141.40
7 purchase totals =	$963.78		$1,033.8943	$1,033.88	$1,033.85	$1,034.10