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	$101.59	7.857%	$109.5719	$109.57	$109.55	$109.60
Purchase #2	$160.32	10.550%	$177.2338	$177.23	$177.25	$177.20
Purchase #3	$230.34	11.309%	$256.3892	$256.39	$256.40	$256.40
Purchase #4	$194.78	13.777%	$221.6148	$221.61	$221.60	$221.60
Purchase #5	$224.45	10.446%	$247.896	$247.90	$247.90	$247.90
Purchase #6	$54.83	7.123%	$58.7355	$58.74	$58.75	$58.70
Purchase #7	$36.40	10.562%	$40.2446	$40.24	$40.25	$40.20
7 purchase totals =	$1,002.71		$1,111.6858	$1,111.68	$1,111.70	$1,111.60