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	$229.42	8.736%	$249.4621	$249.46	$249.45	$249.50
Purchase #2	$37.85	13.844%	$43.09	$43.09	$43.10	$43.10
Purchase #3	$73.83	8.587%	$80.1698	$80.17	$80.15	$80.20
Purchase #4	$190.75	5.824%	$201.8593	$201.86	$201.85	$201.90
Purchase #5	$153.88	12.235%	$172.7072	$172.71	$172.70	$172.70
Purchase #6	$19.72	5.794%	$20.8626	$20.86	$20.85	$20.90
Purchase #7	$225.86	3.813%	$234.472	$234.47	$234.45	$234.50
7 purchase totals =	$931.31		$1,002.6230	$1,002.62	$1,002.55	$1,002.80