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	$224.26	5.195%	$235.9103	$235.91	$235.90	$235.90
Purchase #2	$10.82	7.810%	$11.665	$11.67	$11.65	$11.70
Purchase #3	$27.67	13.487%	$31.4019	$31.40	$31.40	$31.40
Purchase #4	$43.47	8.748%	$47.2728	$47.27	$47.25	$47.30
Purchase #5	$53.57	10.371%	$59.1257	$59.13	$59.15	$59.10
Purchase #6	$135.46	7.555%	$145.694	$145.69	$145.70	$145.70
Purchase #7	$38.79	8.516%	$42.0934	$42.09	$42.10	$42.10
7 purchase totals =	$534.04		$573.1631	$573.16	$573.15	$573.20