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	$176.92	6.596%	$188.5896	$188.59	$188.60	$188.60
Purchase #2	$232.99	9.803%	$255.83	$255.83	$255.85	$255.80
Purchase #3	$46.27	12.670%	$52.1324	$52.13	$52.15	$52.10
Purchase #4	$60.99	6.386%	$64.8848	$64.88	$64.90	$64.90
Purchase #5	$132.50	8.482%	$143.7387	$143.74	$143.75	$143.70
Purchase #6	$44.92	6.442%	$47.8137	$47.81	$47.80	$47.80
Purchase #7	$245.71	13.383%	$278.5934	$278.59	$278.60	$278.60
7 purchase totals =	$940.30		$1,031.5826	$1,031.57	$1,031.65	$1,031.50