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	$140.77	13.739%	$160.1104	$160.11	$160.10	$160.10
Purchase #2	$85.55	4.870%	$89.7163	$89.72	$89.70	$89.70
Purchase #3	$172.53	5.439%	$181.9139	$181.91	$181.90	$181.90
Purchase #4	$150.97	10.638%	$167.0302	$167.03	$167.05	$167.00
Purchase #5	$6.71	11.117%	$7.456	$7.46	$7.45	$7.50
Purchase #6	$228.38	4.554%	$238.7804	$238.78	$238.80	$238.80
Purchase #7	$190.68	6.462%	$203.0017	$203.00	$203.00	$203.00
7 purchase totals =	$975.59		$1,048.0089	$1,048.01	$1,048.00	$1,048.00