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	$237.31	3.599%	$245.8508	$245.85	$245.85	$245.90
Purchase #2	$48.74	5.526%	$51.4334	$51.43	$51.45	$51.40
Purchase #3	$242.88	5.670%	$256.6513	$256.65	$256.65	$256.70
Purchase #4	$198.36	4.323%	$206.9351	$206.94	$206.95	$206.90
Purchase #5	$92.71	13.167%	$104.9171	$104.92	$104.90	$104.90
Purchase #6	$7.28	8.307%	$7.8847	$7.88	$7.90	$7.90
Purchase #7	$192.58	10.713%	$213.2111	$213.21	$213.20	$213.20
7 purchase totals =	$1,019.86		$1,086.8835	$1,086.88	$1,086.90	$1,086.90