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	$87.44	3.758%	$90.726	$90.73	$90.75	$90.70
Purchase #2	$225.93	3.771%	$234.4498	$234.45	$234.45	$234.40
Purchase #3	$39.40	3.865%	$40.9228	$40.92	$40.90	$40.90
Purchase #4	$63.58	13.362%	$72.0756	$72.08	$72.10	$72.10
Purchase #5	$72.26	6.746%	$77.1347	$77.13	$77.15	$77.10
Purchase #6	$205.66	9.845%	$225.9072	$225.91	$225.90	$225.90
Purchase #7	$242.34	9.727%	$265.9124	$265.91	$265.90	$265.90
7 purchase totals =	$936.61		$1,007.1285	$1,007.13	$1,007.15	$1,007.00