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	$132.78	7.518%	$142.7624	$142.76	$142.75	$142.80
Purchase #2	$42.34	11.639%	$47.268	$47.27	$47.25	$47.30
Purchase #3	$78.74	9.520%	$86.236	$86.24	$86.25	$86.20
Purchase #4	$181.58	13.207%	$205.5613	$205.56	$205.55	$205.60
Purchase #5	$159.90	8.406%	$173.3412	$173.34	$173.35	$173.30
Purchase #6	$73.85	12.286%	$82.9232	$82.92	$82.90	$82.90
Purchase #7	$13.59	13.153%	$15.3775	$15.38	$15.40	$15.40
7 purchase totals =	$682.78		$753.4696	$753.47	$753.45	$753.50