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	$154.38	9.338%	$168.796	$168.80	$168.80	$168.80
Purchase #2	$196.91	10.836%	$218.2472	$218.25	$218.25	$218.20
Purchase #3	$5.83	7.505%	$6.2675	$6.27	$6.25	$6.30
Purchase #4	$246.29	3.744%	$255.5111	$255.51	$255.50	$255.50
Purchase #5	$99.95	11.528%	$111.4722	$111.47	$111.45	$111.50
Purchase #6	$43.38	6.373%	$46.1446	$46.14	$46.15	$46.10
Purchase #7	$222.81	3.463%	$230.5259	$230.53	$230.55	$230.50
7 purchase totals =	$969.55		$1,036.9645	$1,036.97	$1,036.95	$1,036.90