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	$131.85	3.835%	$136.9064	$136.91	$136.90	$136.90
Purchase #2	$102.41	13.721%	$116.4617	$116.46	$116.45	$116.50
Purchase #3	$172.83	5.665%	$182.6208	$182.62	$182.60	$182.60
Purchase #4	$198.84	8.568%	$215.8766	$215.88	$215.90	$215.90
Purchase #5	$226.90	5.745%	$239.9354	$239.94	$239.95	$239.90
Purchase #6	$248.48	5.508%	$262.1663	$262.17	$262.15	$262.20
Purchase #7	$18.63	11.780%	$20.8246	$20.82	$20.80	$20.80
7 purchase totals =	$1,099.94		$1,174.7918	$1,174.80	$1,174.75	$1,174.80