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	$164.57	8.700%	$178.8876	$178.89	$178.90	$178.90
Purchase #2	$76.76	7.423%	$82.4579	$82.46	$82.45	$82.50
Purchase #3	$191.52	7.259%	$205.4224	$205.42	$205.40	$205.40
Purchase #4	$248.26	4.343%	$259.0419	$259.04	$259.05	$259.00
Purchase #5	$30.33	3.753%	$31.4683	$31.47	$31.45	$31.50
Purchase #6	$215.71	10.174%	$237.6563	$237.66	$237.65	$237.70
Purchase #7	$77.31	6.462%	$82.3058	$82.31	$82.30	$82.30
7 purchase totals =	$1,004.46		$1,077.2402	$1,077.25	$1,077.20	$1,077.30