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	$106.52	11.386%	$118.6484	$118.65	$118.65	$118.60
Purchase #2	$80.37	11.279%	$89.4349	$89.43	$89.45	$89.40
Purchase #3	$75.30	4.126%	$78.4069	$78.41	$78.40	$78.40
Purchase #4	$156.85	9.712%	$172.0833	$172.08	$172.10	$172.10
Purchase #5	$66.91	4.333%	$69.8092	$69.81	$69.80	$69.80
Purchase #6	$110.81	6.380%	$117.8797	$117.88	$117.90	$117.90
Purchase #7	$55.71	12.779%	$62.8292	$62.83	$62.85	$62.80
7 purchase totals =	$652.47		$709.0916	$709.09	$709.15	$709.00