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	$232.78	9.863%	$255.7391	$255.74	$255.75	$255.70
Purchase #2	$27.59	6.725%	$29.4454	$29.45	$29.45	$29.40
Purchase #3	$131.72	8.762%	$143.2613	$143.26	$143.25	$143.30
Purchase #4	$220.97	3.330%	$228.3283	$228.33	$228.35	$228.30
Purchase #5	$200.61	5.167%	$210.9755	$210.98	$211.00	$211.00
Purchase #6	$147.59	10.343%	$162.8552	$162.86	$162.85	$162.90
Purchase #7	$26.33	9.687%	$28.8806	$28.88	$28.90	$28.90
7 purchase totals =	$987.59		$1,059.4854	$1,059.50	$1,059.55	$1,059.50