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	$54.81	8.577%	$59.5111	$59.51	$59.50	$59.50
Purchase #2	$88.69	7.422%	$95.2726	$95.27	$95.25	$95.30
Purchase #3	$180.80	8.634%	$196.4103	$196.41	$196.40	$196.40
Purchase #4	$215.85	6.770%	$230.463	$230.46	$230.45	$230.50
Purchase #5	$5.58	10.693%	$6.1767	$6.18	$6.20	$6.20
Purchase #6	$120.75	9.513%	$132.2369	$132.24	$132.25	$132.20
Purchase #7	$27.94	12.317%	$31.3814	$31.38	$31.40	$31.40
7 purchase totals =	$694.42		$751.4520	$751.45	$751.45	$751.50