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	$28.33	4.625%	$29.6403	$29.64	$29.65	$29.60
Purchase #2	$224.29	5.869%	$237.4536	$237.45	$237.45	$237.50
Purchase #3	$125.59	12.833%	$141.707	$141.71	$141.70	$141.70
Purchase #4	$222.70	5.511%	$234.973	$234.97	$234.95	$235.00
Purchase #5	$114.95	11.716%	$128.4175	$128.42	$128.40	$128.40
Purchase #6	$89.35	12.530%	$100.5456	$100.55	$100.55	$100.50
Purchase #7	$205.66	10.506%	$227.2666	$227.27	$227.25	$227.30
7 purchase totals =	$1,010.87		$1,100.0036	$1,100.01	$1,099.95	$1,100.00