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	$146.33	10.650%	$161.9141	$161.91	$161.90	$161.90
Purchase #2	$93.86	11.538%	$104.6896	$104.69	$104.70	$104.70
Purchase #3	$225.66	3.497%	$233.5513	$233.55	$233.55	$233.60
Purchase #4	$183.54	13.621%	$208.54	$208.54	$208.55	$208.50
Purchase #5	$135.79	5.727%	$143.5667	$143.57	$143.55	$143.60
Purchase #6	$24.46	12.853%	$27.6038	$27.60	$27.60	$27.60
Purchase #7	$43.77	3.565%	$45.3304	$45.33	$45.35	$45.30
7 purchase totals =	$853.41		$925.1959	$925.19	$925.20	$925.20