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	$158.80	8.242%	$171.8883	$171.89	$171.90	$171.90
Purchase #2	$143.31	11.827%	$160.2593	$160.26	$160.25	$160.30
Purchase #3	$5.50	10.681%	$6.0875	$6.09	$6.10	$6.10
Purchase #4	$12.48	7.302%	$13.3913	$13.39	$13.40	$13.40
Purchase #5	$42.80	6.444%	$45.558	$45.56	$45.55	$45.60
Purchase #6	$228.84	11.784%	$255.8065	$255.81	$255.80	$255.80
Purchase #7	$236.99	7.767%	$255.397	$255.40	$255.40	$255.40
7 purchase totals =	$828.72		$908.3879	$908.40	$908.40	$908.50