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	$217.96	9.430%	$238.5136	$238.51	$238.50	$238.50
Purchase #2	$40.45	8.635%	$43.9429	$43.94	$43.95	$43.90
Purchase #3	$59.35	13.739%	$67.5041	$67.50	$67.50	$67.50
Purchase #4	$119.39	4.524%	$124.7912	$124.79	$124.80	$124.80
Purchase #5	$48.90	10.295%	$53.9343	$53.93	$53.95	$53.90
Purchase #6	$16.84	4.160%	$17.5405	$17.54	$17.55	$17.50
Purchase #7	$71.90	8.636%	$78.1093	$78.11	$78.10	$78.10
7 purchase totals =	$574.79		$624.3359	$624.32	$624.35	$624.20