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	$143.77	10.273%	$158.5395	$158.54	$158.55	$158.50
Purchase #2	$224.95	10.512%	$248.5967	$248.60	$248.60	$248.60
Purchase #3	$71.59	9.197%	$78.1741	$78.17	$78.15	$78.20
Purchase #4	$128.93	10.820%	$142.8802	$142.88	$142.90	$142.90
Purchase #5	$125.51	7.829%	$135.3362	$135.34	$135.35	$135.30
Purchase #6	$82.92	4.619%	$86.7501	$86.75	$86.75	$86.80
Purchase #7	$111.90	5.518%	$118.0746	$118.07	$118.05	$118.10
7 purchase totals =	$889.57		$968.3514	$968.35	$968.35	$968.40