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	$227.26	6.120%	$241.1683	$241.17	$241.15	$241.20
Purchase #2	$97.51	12.519%	$109.7173	$109.72	$109.70	$109.70
Purchase #3	$147.49	12.763%	$166.3141	$166.31	$166.30	$166.30
Purchase #4	$84.34	6.149%	$89.5261	$89.53	$89.55	$89.50
Purchase #5	$76.38	7.859%	$82.3827	$82.38	$82.40	$82.40
Purchase #6	$73.86	12.758%	$83.2831	$83.28	$83.30	$83.30
Purchase #7	$245.50	6.353%	$261.0966	$261.10	$261.10	$261.10
7 purchase totals =	$952.34		$1,033.4882	$1,033.49	$1,033.50	$1,033.50